I am new to Machine Learning.I am working on a project where the machine learning concept need to be applied.
Problem Statement:
I have large number(say 3000)key words.These need to be classified into seven fixed categories.Each category is having training data(sample keywords).I need to come with a algorithm, when a new keyword is passed to that,it should predict to which category this key word belongs to.
I am not aware of which text classification technique need to applied for this.do we have any tools that can be used.
Please help.
Thanks in advance.
This comes under linear classification. You can use naive-bayes classifier for this. Most of the ml frameworks will have an implementation for naive-bayes. ex: mahout
Yes, I would also suggest to use Naive Bayes, which is more or less the baseline classification algorithm here. On the other hand, there are obviously many other algorithms. Random forests and Support Vector Machines come to mind. See http://machinelearningmastery.com/use-random-forest-testing-179-classifiers-121-datasets/ If you use a standard toolkit, such as Weka, Rapidminer, etc. these algorithms should be available. There is also OpenNLP for Java, which comes with a maximum entropy classifier.
You could use the Word2Vec Word Cosine distance between descriptions of each your category and keywords in the dataset and then simple match each keyword to a category with the closest distance
Alternatively, you could create a training dataset from already matched to category, keywords and use any ML classifier, for example, based on artificial neural networks by using vectors of keywords Cosine distances to each category as an input to your model. But it could require a big quantity of data for training to reach good accuracy. For example, the MNIST dataset contains 70000 of the samples and it allowed me reach 99,62% model's cross validation accuracy with a simple CNN, for another dataset with only 2000 samples I was able reached only about 90% accuracy
There are many classification algorithms. Your example looks to be a text classification problems - some good classifiers to try out would be SVM and naive bayes. For SVM, liblinear and libshorttext classifiers are good options (and have been used in many industrial applcitions):
liblinear: https://www.csie.ntu.edu.tw/~cjlin/liblinear/
libshorttext:https://www.csie.ntu.edu.tw/~cjlin/libshorttext/
They are also included with ML tools such as scikit-learna and WEKA.
With classifiers, it is still some operation to build and validate a pratically useful classifier. One of the challenges is to mix
discrete (boolean and enumerable)
and continuous ('numbers')
predictive variables seamlessly. Some algorithmic preprocessing is generally necessary.
Neural networks do offer the possibility of using both types of variables. However, they require skilled data scientists to yield good results. A straight-forward option is to use an online classifier web service like Insight Classifiers to build and validate a classifier in one go. N-fold cross validation is being used there.
You can represent the presence or absence of each word in a separate column. The outcome variable is desired category.
I would like to find the factors that contribute to a particular event happening. However that event occurs only about 1% of the time. So if I have a class attribute called event_happened, 99% of the time the value is 0, and 1 only 1% of the time. Traditional data mining predictions techniques (decision tree, naive bayes etc) don't seem to be working in this case. Any suggestions as to how should go about mining this dataset? Thanks.
This is the typical description of the task Anomaly detection task
It defines its own group of algorithms:
In data mining, anomaly detection (or outlier detection) is the identification of items, events or observations which do not conform to an expected pattern or other items in a dataset.
And a statement about the possible approaches:
Three broad categories of anomaly detection techniques exist. Unsupervised anomaly detection techniques detect anomalies in an unlabeled test data set under the assumption that the majority of the instances in the data set are normal by looking for instances that seem to fit least to the remainder of the data set. Supervised anomaly detection techniques require a data set that has been labeled as "normal" and "abnormal" and involves training a classifier (the key difference to many other statistical classification problems is the inherent unbalanced nature of outlier detection). Semi-supervised anomaly detection techniques construct a model representing normal behavior from a given normal training data set, and then testing the likelihood of a test instance to be generated by the learned model.
What you would choose is a question of personal flavor.
These approaches will help "learn" to find out outlier events; then the model that "predicts" them will define the factors that you are interested in.
lets say my attributes are hour_of_the day, day_of_the_week, state, customer_age, customer_gender etc. And I want to find out which of these factors contribute to my event occurring.
Based on this answer, I believe you need classification, but your result will be the model itself.
So, you perform, say, logistic regression, but your features are the data attributes themselves(some literature doesn't even separate features and attributes).
You have to somehow normalize this data. This can be tricky. I would go for boolean features(say hour_of_event==00, hour_of_event==01, hour_of_event==02,...)
Then, you apply any classification model, you end up with weights against each of the attributes. The attributes with (the highest weights will be the factors that you need).
This is an unbalanced classification problem.
I'm pretty sure I have seen some surveys and overview articles on methods that can handle unbalanced data well. You should research this term ("skew" is a bit broad, and may not get you the results you are looking for).
I am using a Naive Bayes Classifier to categorize several thousand documents into 30 different categories. I have implemented a Naive Bayes Classifier, and with some feature selection (mostly filtering useless words), I've gotten about a 30% test accuracy, with 45% training accuracy. This is significantly better than random, but I want it to be better.
I've tried implementing AdaBoost with NB, but it does not appear to give appreciably better results (the literature seems split on this, some papers say AdaBoost with NB doesn't give better results, others do). Do you know of any other extensions to NB that may possibly give better accuracy?
In my experience, properly trained Naive Bayes classifiers are usually astonishingly accurate (and very fast to train--noticeably faster than any classifier-builder i have everused).
so when you want to improve classifier prediction, you can look in several places:
tune your classifier (adjusting the classifier's tunable paramaters);
apply some sort of classifier combination technique (eg,
ensembling, boosting, bagging); or you can
look at the data fed to the classifier--either add more data,
improve your basic parsing, or refine the features you select from
the data.
w/r/t naive Bayesian classifiers, parameter tuning is limited; i recommend to focus on your data--ie, the quality of your pre-processing and the feature selection.
I. Data Parsing (pre-processing)
i assume your raw data is something like a string of raw text for each data point, which by a series of processing steps you transform each string into a structured vector (1D array) for each data point such that each offset corresponds to one feature (usually a word) and the value in that offset corresponds to frequency.
stemming: either manually or by using a stemming library? the popular open-source ones are Porter, Lancaster, and Snowball. So for
instance, if you have the terms programmer, program, progamming,
programmed in a given data point, a stemmer will reduce them to a
single stem (probably program) so your term vector for that data
point will have a value of 4 for the feature program, which is
probably what you want.
synonym finding: same idea as stemming--fold related words into a single word; so a synonym finder can identify developer, programmer,
coder, and software engineer and roll them into a single term
neutral words: words with similar frequencies across classes make poor features
II. Feature Selection
consider a prototypical use case for NBCs: filtering spam; you can quickly see how it fails and just as quickly you can see how to improve it. For instance, above-average spam filters have nuanced features like: frequency of words in all caps, frequency of words in title, and the occurrence of exclamation point in the title. In addition, the best features are often not single words but e.g., pairs of words, or larger word groups.
III. Specific Classifier Optimizations
Instead of 30 classes use a 'one-against-many' scheme--in other words, you begin with a two-class classifier (Class A and 'all else') then the results in the 'all else' class are returned to the algorithm for classification into Class B and 'all else', etc.
The Fisher Method (probably the most common way to optimize a Naive Bayes classifier.) To me,
i think of Fisher as normalizing (more correctly, standardizing) the input probabilities An NBC uses the feature probabilities to construct a 'whole-document' probability. The Fisher Method calculates the probability of a category for each feature of the document then combines these feature probabilities and compares that combined probability with the probability of a random set of features.
I would suggest using a SGDClassifier as in this and tune it in terms of regularization strength.
Also try to tune the formula in TFIDF you're using by tuning the parameters of TFIFVectorizer.
I usually see that for text classification problems SVM or Logistic Regressioin when trained one-versus-all outperforms NB. As you can see in this nice article by Stanford people for longer documents SVM outperforms NB. The code for the paper which uses a combination of SVM and NB (NBSVM) is here.
Second, tune your TFIDF formula (e.g. sublinear tf, smooth_idf).
Normalize your samples with l2 or l1 normalization (default in Tfidfvectorization) because it compensates for different document lengths.
Multilayer Perceptron, usually gets better results than NB or SVM because of the non-linearity introduced which is inherent to many text classification problems. I have implemented a highly parallel one using Theano/Lasagne which is easy to use and downloadable here.
Try to tune your l1/l2/elasticnet regularization. It makes a huge difference in SGDClassifier/SVM/Logistic Regression.
Try to use n-grams which is configurable in tfidfvectorizer.
If your documents have structure (e.g. have titles) consider using different features for different parts. For example add title_word1 to your document if word1 happens in the title of the document.
Consider using the length of the document as a feature (e.g. number of words or characters).
Consider using meta information about the document (e.g. time of creation, author name, url of the document, etc.).
Recently Facebook published their FastText classification code which performs very well across many tasks, be sure to try it.
Using Laplacian Correction along with AdaBoost.
In AdaBoost, first a weight is assigned to each data tuple in the training dataset. The intial weights are set using the init_weights method, which initializes each weight to be 1/d, where d is the size of the training data set.
Then, a generate_classifiers method is called, which runs k times, creating k instances of the Naïve Bayes classifier. These classifiers are then weighted, and the test data is run on each classifier. The sum of the weighted "votes" of the classifiers constitutes the final classification.
Improves Naive Bayes classifier for general cases
Take the logarithm of your probabilities as input features
We change the probability space to log probability space since we calculate the probability by multiplying probabilities and the result will be very small. when we change to log probability features, we can tackle the under-runs problem.
Remove correlated features.
Naive Byes works based on the assumption of independence when we have a correlation between features which means one feature depends on others then our assumption will fail.
More about correlation can be found here
Work with enough data not the huge data
naive Bayes require less data than logistic regression since it only needs data to understand the probabilistic relationship of each attribute in isolation with the output variable, not the interactions.
Check zero frequency error
If the test data set has zero frequency issue, apply smoothing techniques “Laplace Correction” to predict the class of test data set.
More than this is well described in the following posts
Please refer below posts.
machinelearningmastery site post
Analyticvidhya site post
keeping the n size small also make NB to give high accuracy result. and at the core, as the n size increase its accuracy degrade,
Select features which have less correlation between them. And try using different combination of features at a time.
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Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.)
How do I know which classifier I should use?
Decision tree
SVM
Bayesian
Neural network
K-nearest neighbors
Q-learning
Genetic algorithm
Markov decision processes
Convolutional neural networks
Linear regression or logistic regression
Boosting, bagging, ensambling
Random hill climbing or simulated annealing
...
In which cases is one of these the "natural" first choice, and what are the principles for choosing that one?
Examples of the type of answers I'm looking for (from Manning et al.'s Introduction to Information Retrieval book):
a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes).
I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.
b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability.
What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though.
Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)?
First of all, you need to identify your problem. It depends upon what kind of data you have and what your desired task is.
If you are Predicting Category :
You have Labeled Data
You need to follow Classification Approach and its algorithms
You don't have Labeled Data
You need to go for Clustering Approach
If you are Predicting Quantity :
You need to go for Regression Approach
Otherwise
You can go for Dimensionality Reduction Approach
There are different algorithms within each approach mentioned above. The choice of a particular algorithm depends upon the size of the dataset.
Source: http://scikit-learn.org/stable/tutorial/machine_learning_map/
Model selection using cross validation may be what you need.
Cross validation
What you do is simply to split your dataset into k non-overlapping subsets (folds), train a model using k-1 folds and predict its performance using the fold you left out. This you do for each possible combination of folds (first leave 1st fold out, then 2nd, ... , then kth, and train with the remaining folds). After finishing, you estimate the mean performance of all folds (maybe also the variance/standard deviation of the performance).
How to choose the parameter k depends on the time you have. Usual values for k are 3, 5, 10 or even N, where N is the size of your data (that's the same as leave-one-out cross validation). I prefer 5 or 10.
Model selection
Let's say you have 5 methods (ANN, SVM, KNN, etc) and 10 parameter combinations for each method (depending on the method). You simply have to run cross validation for each method and parameter combination (5 * 10 = 50) and select the best model, method and parameters. Then you re-train with the best method and parameters on all your data and you have your final model.
There are some more things to say. If, for example, you use a lot of methods and parameter combinations for each, it's very likely you will overfit. In cases like these, you have to use nested cross validation.
Nested cross validation
In nested cross validation, you perform cross validation on the model selection algorithm.
Again, you first split your data into k folds. After each step, you choose k-1 as your training data and the remaining one as your test data. Then you run model selection (the procedure I explained above) for each possible combination of those k folds. After finishing this, you will have k models, one for each combination of folds. After that, you test each model with the remaining test data and choose the best one. Again, after having the last model you train a new one with the same method and parameters on all the data you have. That's your final model.
Of course, there are many variations of these methods and other things I didn't mention. If you need more information about these look for some publications about these topics.
The book "OpenCV" has a great two pages on this on pages 462-463. Searching the Amazon preview for the word "discriminative" (probably google books also) will let you see the pages in question. These two pages are the greatest gem I have found in this book.
In short:
Boosting - often effective when a large amount of training data is available.
Random trees - often very effective and can also perform regression.
K-nearest neighbors - simplest thing you can do, often effective but slow and requires lots of memory.
Neural networks - Slow to train but very fast to run, still optimal performer for letter recognition.
SVM - Among the best with limited data, but losing against boosting or random trees only when large data sets are available.
Things you might consider in choosing which algorithm to use would include:
Do you need to train incrementally (as opposed to batched)?
If you need to update your classifier with new data frequently (or you have tons of data), you'll probably want to use Bayesian. Neural nets and SVM need to work on the training data in one go.
Is your data composed of categorical only, or numeric only, or both?
I think Bayesian works best with categorical/binomial data. Decision trees can't predict numerical values.
Does you or your audience need to understand how the classifier works?
Use Bayesian or decision trees, since these can be easily explained to most people. Neural networks and SVM are "black boxes" in the sense that you can't really see how they are classifying data.
How much classification speed do you need?
SVM's are fast when it comes to classifying since they only need to determine which side of the "line" your data is on. Decision trees can be slow especially when they're complex (e.g. lots of branches).
Complexity.
Neural nets and SVMs can handle complex non-linear classification.
As Prof Andrew Ng often states: always begin by implementing a rough, dirty algorithm, and then iteratively refine it.
For classification, Naive Bayes is a good starter, as it has good performances, is highly scalable and can adapt to almost any kind of classification task. Also 1NN (K-Nearest Neighbours with only 1 neighbour) is a no-hassle best fit algorithm (because the data will be the model, and thus you don't have to care about the dimensionality fit of your decision boundary), the only issue is the computation cost (quadratic because you need to compute the distance matrix, so it may not be a good fit for high dimensional data).
Another good starter algorithm is the Random Forests (composed of decision trees), this is highly scalable to any number of dimensions and has generally quite acceptable performances. Then finally, there are genetic algorithms, which scale admirably well to any dimension and any data with minimal knowledge of the data itself, with the most minimal and simplest implementation being the microbial genetic algorithm (only one line of C code! by Inman Harvey in 1996), and one of the most complex being CMA-ES and MOGA/e-MOEA.
And remember that, often, you can't really know what will work best on your data before you try the algorithms for real.
As a side-note, if you want a theoretical framework to test your hypothesis and algorithms theoretical performances for a given problem, you can use the PAC (Probably approximately correct) learning framework (beware: it's very abstract and complex!), but to summary, the gist of PAC learning says that you should use the less complex, but complex enough (complexity being the maximum dimensionality that the algo can fit) algorithm that can fit your data. In other words, use the Occam's razor.
Sam Roweis used to say that you should try naive Bayes, logistic regression, k-nearest neighbour and Fisher's linear discriminant before anything else.
My take on it is that you always run the basic classifiers first to get some sense of your data. More often than not (in my experience at least) they've been good enough.
So, if you have supervised data, train a Naive Bayes classifier. If you have unsupervised data, you can try k-means clustering.
Another resource is one of the lecture videos of the series of videos Stanford Machine Learning, which I watched a while back. In video 4 or 5, I think, the lecturer discusses some generally accepted conventions when training classifiers, advantages/tradeoffs, etc.
You should always keep into account the inference vs prediction trade-off.
If you want to understand the complex relationship that is occurring in your data then you should go with a rich inference algorithm (e.g. linear regression or lasso). On the other hand, if you are only interested in the result you can go with high dimensional and more complex (but less interpretable) algorithms, like neural networks.
Selection of Algorithm is depending upon the scenario and the type and size of data set.
There are many other factors.
This is a brief cheat sheet for basic machine learning.
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In terms of artificial intelligence and machine learning, what is the difference between supervised and unsupervised learning?
Can you provide a basic, easy explanation with an example?
Since you ask this very basic question, it looks like it's worth specifying what Machine Learning itself is.
Machine Learning is a class of algorithms which is data-driven, i.e. unlike "normal" algorithms it is the data that "tells" what the "good answer" is. Example: a hypothetical non-machine learning algorithm for face detection in images would try to define what a face is (round skin-like-colored disk, with dark area where you expect the eyes etc). A machine learning algorithm would not have such coded definition, but would "learn-by-examples": you'll show several images of faces and not-faces and a good algorithm will eventually learn and be able to predict whether or not an unseen image is a face.
This particular example of face detection is supervised, which means that your examples must be labeled, or explicitly say which ones are faces and which ones aren't.
In an unsupervised algorithm your examples are not labeled, i.e. you don't say anything. Of course, in such a case the algorithm itself cannot "invent" what a face is, but it can try to cluster the data into different groups, e.g. it can distinguish that faces are very different from landscapes, which are very different from horses.
Since another answer mentions it (though, in an incorrect way): there are "intermediate" forms of supervision, i.e. semi-supervised and active learning. Technically, these are supervised methods in which there is some "smart" way to avoid a large number of labeled examples. In active learning, the algorithm itself decides which thing you should label (e.g. it can be pretty sure about a landscape and a horse, but it might ask you to confirm if a gorilla is indeed the picture of a face). In semi-supervised learning, there are two different algorithms which start with the labeled examples, and then "tell" each other the way they think about some large number of unlabeled data. From this "discussion" they learn.
Supervised learning is when the data you feed your algorithm with is "tagged" or "labelled", to help your logic make decisions.
Example: Bayes spam filtering, where you have to flag an item as spam to refine the results.
Unsupervised learning are types of algorithms that try to find correlations without any external inputs other than the raw data.
Example: data mining clustering algorithms.
Supervised learning
Applications in which the training data comprises examples of the input vectors along with their corresponding target vectors are known as supervised learning problems.
Unsupervised learning
In other pattern recognition problems, the training data consists of a set of input vectors x without any corresponding target values. The goal in such unsupervised learning problems may be to discover groups of similar examples within the data, where it is called clustering
Pattern Recognition and Machine Learning (Bishop, 2006)
In supervised learning, the input x is provided with the expected outcome y (i.e., the output the model is supposed to produce when the input is x), which is often called the "class" (or "label") of the corresponding input x.
In unsupervised learning, the "class" of an example x is not provided. So, unsupervised learning can be thought of as finding "hidden structure" in unlabelled data set.
Approaches to supervised learning include:
Classification (1R, Naive Bayes, decision tree learning algorithm, such
as ID3 CART, and so on)
Numeric Value Prediction
Approaches to unsupervised learning include:
Clustering (K-means, hierarchical clustering)
Association Rule Learning
I can tell you an example.
Suppose you need to recognize which vehicle is a car and which one is a motorcycle.
In the supervised learning case, your input (training) dataset needs to be labelled, that is, for each input element in your input (training) dataset, you should specify if it represents a car or a motorcycle.
In the unsupervised learning case, you do not label the inputs. The unsupervised model clusters the input into clusters based e.g. on similar features/properties. So, in this case, there is are no labels like "car".
For instance, very often training a neural network is supervised learning: you're telling the network to which class corresponds the feature vector you're feeding.
Clustering is unsupervised learning: you let the algorithm decide how to group samples into classes that share common properties.
Another example of unsupervised learning is Kohonen's self organizing maps.
I have always found the distinction between unsupervised and supervised learning to be arbitrary and a little confusing. There is no real distinction between the two cases, instead there is a range of situations in which an algorithm can have more or less 'supervision'. The existence of semi-supervised learning is an obvious examples where the line is blurred.
I tend to think of supervision as giving feedback to the algorithm about what solutions should be preferred. For a traditional supervised setting, such as spam detection, you tell the algorithm "don't make any mistakes on the training set"; for a traditional unsupervised setting, such as clustering, you tell the algorithm "points that are close to each other should be in the same cluster". It just so happens that, the first form of feedback is a lot more specific than the latter.
In short, when someone says 'supervised', think classification, when they say 'unsupervised' think clustering and try not to worry too much about it beyond that.
Supervised Learning
Supervised learning is based on training a data sample
from data source with correct classification already assigned.
Such techniques are utilized in feedforward or MultiLayer
Perceptron (MLP) models. These MLP has three distinctive
characteristics:
One or more layers of hidden neurons that are not part of the input
or output layers of the network that enable the network to learn and
solve any complex problems
The nonlinearity reflected in the neuronal activity is
differentiable and,
The interconnection model of the network exhibits a high degree of
connectivity.
These characteristics along with learning through training
solve difficult and diverse problems. Learning through
training in a supervised ANN model also called as error backpropagation algorithm. The error correction-learning
algorithm trains the network based on the input-output
samples and finds error signal, which is the difference of the
output calculated and the desired output and adjusts the
synaptic weights of the neurons that is proportional to the
product of the error signal and the input instance of the
synaptic weight. Based on this principle, error back
propagation learning occurs in two passes:
Forward Pass:
Here, input vector is presented to the network. This input signal propagates forward, neuron by neuron through the network and emerges at the output end of
the network as output signal: y(n) = φ(v(n)) where v(n) is the induced local field of a neuron defined by v(n) =Σ w(n)y(n). The output that is calculated at the output layer o(n) is compared with the desired response d(n) and finds the error e(n) for that neuron. The synaptic weights of the network during this pass are remains same.
Backward Pass:
The error signal that is originated at the output neuron of that layer is propagated backward through network. This calculates the local gradient for each neuron in each layer and allows the synaptic weights of the network to undergo changes in accordance with the delta rule as:
Δw(n) = η * δ(n) * y(n).
This recursive computation is continued, with forward pass followed by the backward pass for each input pattern till the network is converged.
Supervised learning paradigm of an ANN is efficient and finds solutions to several linear and non-linear problems such as classification, plant control, forecasting, prediction, robotics etc.
Unsupervised Learning
Self-Organizing neural networks learn using unsupervised learning algorithm to identify hidden patterns in unlabelled input data. This unsupervised refers to the ability to learn and organize information without providing an error signal to evaluate the potential solution. The lack of direction for the learning algorithm in unsupervised learning can sometime be advantageous, since it lets the algorithm to look back for patterns that have not been previously considered. The main characteristics of Self-Organizing Maps (SOM) are:
It transforms an incoming signal pattern of arbitrary dimension into
one or 2 dimensional map and perform this transformation adaptively
The network represents feedforward structure with a single
computational layer consisting of neurons arranged in rows and
columns. At each stage of representation, each input signal is kept
in its proper context and,
Neurons dealing with closely related pieces of information are close
together and they communicate through synaptic connections.
The computational layer is also called as competitive layer since the neurons in the layer compete with each other to become active. Hence, this learning algorithm is called competitive algorithm. Unsupervised algorithm in SOM
works in three phases:
Competition phase:
for each input pattern x, presented to the network, inner product with synaptic weight w is calculated and the neurons in the competitive layer finds a discriminant function that induce competition among the neurons and the synaptic weight vector that is close to the input vector in the Euclidean distance is announced as winner in the competition. That neuron is called best matching neuron,
i.e. x = arg min ║x - w║.
Cooperative phase:
the winning neuron determines the center of a topological neighborhood h of cooperating neurons. This is performed by the lateral interaction d among the
cooperative neurons. This topological neighborhood reduces its size over a time period.
Adaptive phase:
enables the winning neuron and its neighborhood neurons to increase their individual values of the discriminant function in relation to the input pattern
through suitable synaptic weight adjustments,
Δw = ηh(x)(x –w).
Upon repeated presentation of the training patterns, the synaptic weight vectors tend to follow the distribution of the input patterns due to the neighborhood updating and thus ANN learns without supervisor.
Self-Organizing Model naturally represents the neuro-biological behavior, and hence is used in many real world applications such as clustering, speech recognition, texture segmentation, vector coding etc.
Reference.
There are many answers already which explain the differences in detail. I found these gifs on codeacademy and they often help me explain the differences effectively.
Supervised Learning
Notice that the training images have labels here and that the model is learning the names of the images.
Unsupervised Learning
Notice that what's being done here is just grouping(clustering) and that the model doesn't know anything about any image.
Machine learning:
It explores the study and construction of algorithms that can learn from and make predictions on data.Such algorithms operate by building a model from example inputs in order to make data-driven predictions or decisions expressed as outputs,rather than following strictly static program instructions.
Supervised learning:
It is the machine learning task of inferring a function from labeled training data.The training data consist of a set of training examples. In supervised learning, each example is a pair consisting of an input object (typically a vector) and a desired output value (also called the supervisory signal). A supervised learning algorithm analyzes the training data and produces an inferred function, which can be used for mapping new examples.
The computer is presented with example inputs and their desired outputs, given by a "teacher", and the goal is to learn a general rule that maps inputs to outputs.Specifically, a supervised learning algorithm takes a known set of input data and known responses to the data (output), and trains a model to generate reasonable predictions for the response to new data.
Unsupervised learning:
It is learning without a teacher. One basic
thing that you might want to do with data is to visualize it. It is the machine learning task of inferring a function to describe hidden structure from unlabeled data. Since the examples given to the learner are unlabeled, there is no error or reward signal to evaluate a potential solution. This distinguishes unsupervised learning from supervised learning. Unsupervised learning uses procedures that attempt to find natural partitions
of patterns.
With unsupervised learning there is no feedback based on the prediction results, i.e., there is no teacher to correct you.Under the Unsupervised learning methods no labeled examples are provided and there is no notion of the output during the learning process. As a result, it is up to the learning scheme/model to find patterns or discover the groups of the input data
You should use unsupervised learning methods when you need a large
amount of data to train your models, and the willingness and ability
to experiment and explore, and of course a challenge that isn’t well
solved via more-established methods.With unsupervised learning it is
possible to learn larger and more complex models than with supervised
learning.Here is a good example on it
.
Supervised Learning: You give variously labelled example data as input, along with the correct answers. This algorithm will learn from it, and start predicting correct results based on the inputs thereafter. Example: Email Spam filter
Unsupervised Learning: You just give data and don't tell anything - like labels or correct answers. Algorithm automatically analyses patterns in the data. Example: Google News
Supervised learning:
say a kid goes to kinder-garden. here teacher shows him 3 toys-house,ball and car. now teacher gives him 10 toys.
he will classify them in 3 box of house,ball and car based on his previous experience.
so kid was first supervised by teachers for getting right answers for few sets. then he was tested on unknown toys.
Unsupervised learning:
again kindergarten example.A child is given 10 toys. he is told to segment similar ones.
so based on features like shape,size,color,function etc he will try to make 3 groups say A,B,C and group them.
The word Supervise means you are giving supervision/instruction to machine to help it find answers. Once it learns instructions, it can easily predict for new case.
Unsupervised means there is no supervision or instruction how to find answers/labels and machine will use its intelligence to find some pattern in our data. Here it will not make prediction, it will just try to find clusters which has similar data.
Supervised learning, given the data with an answer.
Given email labeled as spam/not spam, learn a spam filter.
Given a dataset of patients diagnosed as either having diabetes or not, learn to classify new patients as having diabetes or not.
Unsupervised learning, given the data without an answer, let the pc to group things.
Given a set of news articles found on the web, group the into set of articles about the same story.
Given a database of custom data, automatically discover market segments and group customers into different market segments.
Reference
Supervised Learning
In this, every input pattern that is used to train the network is
associated with an output pattern, which is the target or the desired
pattern. A teacher is assumed to be present during the learning
process, when a comparison is made between the network's computed
output and the correct expected output, to determine the error. The
error can then be used to change network parameters, which result in
an improvement in performance.
Unsupervised Learning
In this learning method, the target output is not presented to the
network. It is as if there is no teacher to present the desired
pattern and hence, the system learns of its own by discovering and
adapting to structural features in the input patterns.
I'll try to keep it simple.
Supervised Learning: In this technique of learning, we are given a data set and the system already knows the correct output of the data set. So here, our system learns by predicting a value of its own. Then, it does an accuracy check by using a cost function to check how close its prediction was to the actual output.
Unsupervised Learning: In this approach, we have little or no knowledge of what our result would be. So instead, we derive structure from the data where we don't know effect of variable.
We make structure by clustering the data based on relationship among the variable in data.
Here, we don't have a feedback based on our prediction.
Supervised learning
You have input x and a target output t. So you train the algorithm to generalize to the missing parts. It is supervised because the target is given. You are the supervisor telling the algorithm: For the example x, you should output t!
Unsupervised learning
Although segmentation, clustering and compression are usually counted in this direction, I have a hard time to come up with a good definition for it.
Let's take auto-encoders for compression as an example. While you only have the input x given, it is the human engineer how tells the algorithm that the target is also x. So in some sense, this is not different from supervised learning.
And for clustering and segmentation, I'm not too sure if it really fits the definition of machine learning (see other question).
Supervised Learning: You have labeled data and have to learn from that. e.g house data along with price and then learn to predict price
Unsupervised learning: you have to find the trend and then predict, no prior labels given.
e.g different people in the class and then a new person comes so what group does this new student belong to.
In Supervised Learning we know what the input and output should be. For example , given a set of cars. We have to find out which ones red and which ones blue.
Whereas, Unsupervised learning is where we have to find out the answer with a very little or without any idea about how the output should be. For example, a learner might be able to build a model that detects when people are smiling based on correlation of facial patterns and words such as "what are you smiling about?".
Supervised learning can label a new item into one of the trained labels based on learning during training. You need to provide large numbers of training data set, validation data set and test data set. If you provide say pixel image vectors of digits along with training data with labels, then it can identify the numbers.
Unsupervised learning does not require training data-sets. In unsupervised learning it can group items into different clusters based on the difference in the input vectors. If you provide pixel image vectors of digits and ask it to classify into 10 categories, it may do that. But it does know how to labels it as you have not provided training labels.
Supervised Learning is basically where you have input variables(x) and output variable(y) and use algorithm to learn the mapping function from input to the output. The reason why we called this as supervised is because algorithm learns from the training dataset, the algorithm iteratively makes predictions on the training data.
Supervised have two types-Classification and Regression.
Classification is when the output variable is category like yes/no, true/false.
Regression is when the output is real values like height of person, Temperature etc.
UN supervised learning is where we have only input data(X) and no output variables.
This is called an unsupervised learning because unlike supervised learning above there is no correct answers and there is no teacher. Algorithms are left to their own devises to discover and present the interesting structure in the data.
Types of unsupervised learning are clustering and Association.
Supervised Learning is basically a technique in which the training data from which the machine learns is already labelled that is suppose a simple even odd number classifier where you have already classified the data during training . Therefore it uses "LABELLED" data.
Unsupervised learning on the contrary is a technique in which the machine by itself labels the data . Or you can say its the case when the machine learns by itself from scratch.
In Simple
Supervised learning is type of machine learning problem in which we have some labels and by using that labels we implement algorithm such as regression and classification .Classification is applied where our output is like in the form of
0 or 1 ,true/false,yes/no. and regression is applied where out put a real value such a house of price
Unsupervised Learning is a type of machine learning problem in which we don't have any labels means we have some data only ,unstructured data and we have to cluster the data (grouping of data)using various unsupervised algorithm
Supervised Machine Learning
"The process of an algorithm learning from training dataset and
predict the output. "
Accuracy of predicted output directly proportional to the training data (length)
Supervised learning is where you have input variables (x) (training dataset) and an output variable (Y) (testing dataset) and you use an algorithm to learn the mapping function from the input to the output.
Y = f(X)
Major types:
Classification (discrete y-axis)
Predictive (continuous y-axis)
Algorithms:
Classification Algorithms:
Neural Networks
Naïve Bayes classifiers
Fisher linear discriminant
KNN
Decision Tree
Super Vector Machines
Predictive Algorithms:
Nearest neighbor
Linear Regression,Multi Regression
Application areas:
Classifying emails as spam
Classifying whether patient has
disease or not
Voice Recognition
Predict the HR select particular candidate or not
Predict the stock market price
Supervised learning:
A supervised learning algorithm analyzes the training data and produces an inferred function, which can be used for mapping new examples.
We provide training data and we know correct output for a certain input
We know relation between input and output
Categories of problem:
Regression: Predict results within a continuous output => map input variables to some continuous function.
Example:
Given a picture of a person, predict his age
Classification: Predict results in a discrete output => map input variables into discrete categories
Example:
Is this tumer cancerous?
Unsupervised learning:
Unsupervised learning learns from test data that has not been labeled, classified or categorized. Unsupervised learning identifies commonalities in the data and reacts based on the presence or absence of such commonalities in each new piece of data.
We can derive this structure by clustering the data based on relationships among the variables in the data.
There is no feedback based on the prediction results.
Categories of problem:
Clustering: is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense) to each other than to those in other groups (clusters)
Example:
Take a collection of 1,000,000 different genes, and find a way to automatically group these genes into groups that are somehow similar or related by different variables, such as lifespan, location, roles, and so on.
Popular use cases are listed here.
Difference between classification and clustering in data mining?
References:
Supervised_learning
Unsupervised_learning
machine-learning from coursera
towardsdatascience
Supervised Learning
Unsupervised Learning
Example:
Supervised Learning:
One bag with apple
One bag with orange
=> build model
One mixed bag of apple and orange.
=> Please classify
Unsupervised Learning:
One mixed bag of apple and orange.
=> build model
Another mixed bag
=> Please classify
In simple words.. :) It's my understanding, feel free to correct.
Supervised learning is, we know what we are predicting on the basis of provided data. So we have a column in the dataset which needs to be predicated.
Unsupervised learning is, we try to extract meaning out of the provided dataset. We don't have clarity on what to be predicted. So question is why we do this?.. :) Answer is - the outcome of Unsupervised learning is groups/clusters(similar data together). So if we receive any new data then we associate that with the identified cluster/group and understand it's features.
I hope it will help you.
supervised learning
supervised learning is where we know the output of the raw input, i.e the data is labelled so that during the training of machine learning model it will understand what it need to detect in the give output, and it will guide the system during the training to detect the pre-labelled objects on that basis it will detect the similar objects which we have provided in training.
Here the algorithms will know what's the structure and pattern of data. Supervised learning is used for classification
As an example, we can have a different objects whose shapes are square, circle, trianle our task is to arrange the same types of shapes
the labelled dataset have all the shapes labelled, and we will train the machine learning model on that dataset, on the based of training dateset it will start detecting the shapes.
Un-supervised learning
Unsupervised learning is a unguided learning where the end result is not known, it will cluster the dataset and based on similar properties of the object it will divide the objects on different bunches and detect the objects.
Here algorithms will search for the different pattern in the raw data, and based on that it will cluster the data. Un-supervised learning is used for clustering.
As an example, we can have different objects of multiple shapes square, circle, triangle, so it will make the bunches based on the object properties, if a object has four sides it will consider it square, and if it have three sides triangle and if no sides than circle, here the the data is not labelled, it will learn itself to detect the various shapes
Machine learning is a field where you are trying to make machine to mimic the human behavior.
You train machine just like a baby.The way humans learn, identify features, recognize patterns and train himself, same way you train machine by feeding data with various features. Machine algorithm identify the pattern within the data and classify it into particular category.
Machine learning broadly divided into two category, supervised and unsupervised learning.
Supervised learning is the concept where you have input vector / data with corresponding target value (output).On the other hand unsupervised learning is the concept where you only have input vectors / data without any corresponding target value.
An example of supervised learning is handwritten digits recognition where you have image of digits with corresponding digit [0-9], and an example of unsupervised learning is grouping customers by purchasing behavior.