Is it possible to predict input data by providing output label on a trained model?
The question doesn't really make sense.
We use the terms input and output to describe the data w.r.t. the problem we are trying to solve.
For example, given a latitude on the earth's surface, it's possible to create a model to try to predict the average temperature in August. Here the input is the latitude and the output is the avg temperature. So, it is of course possible, to try to reverse this and instead frame the problem so as to try to train a model to predict the latitude of a place given it's avg temp in august. BUT in doing so, you have, by definition, changed the input and output around. Latitude is now the output and temp the input.
Input 5+2 gives Output 7
Input 6+1 gives Output 7
Input 4+3 gives Output 7.
As you see in the example above it is easy given two numbers and an operation to get a number uniquely. However starting from number 7 can you uniquely predict which were the two numbers that gave 7?
You may run into these sort of problems. However if it is one to one and onto function (bijective), then you might be able to reverse it. Off course you will have to reverse the labels of input and output.
Related
I have EEG data, for which I want to calculate the peaks' amplitudes and latencies. I'm working with MNE, and found the method get_peak in the Evoked object. However, I want to find peaks on epochs data (not averaged). How can I do it? I didn't see similar functions for the epochs object. I would prefer to do it through MNE, but other python libraries can also work. It's important that there is an option to get the amplitude and latency of the peaks, and choose a time window for detection.
In addition, I didn't understand if the get_peak returns only the highest peak, or something else? If there is more than one peak.
Thanks!
You can create an Evoked data structure from a single trial by just selecting a single trial from your Epochs structure and then applying .average(), e.g., as follows:
tmp_evoked = all_epochs[subj][cond][trial].average()
The above assumes you have an all_epochs object organized as trials within conditions within subjects (i.e., you're working at the group level). If your Epochs object has only one subject, then it would just be:
tmp_evoked = all_epochs[cond][trial].average()
You can further refine this to find the peak at only one channel as:
tmp_evoked = all_epochs[subj][cond][trial].pick(chan).average()
In a database there are time-series data with records:
device - timestamp - temperature - min limit - max limit
device - timestamp - temperature - min limit - max limit
device - timestamp - temperature - min limit - max limit
...
For every device there are 4 hours of time series data (with an interval of 5 minutes) before an alarm was raised and 4 hours of time series data (again with an interval of 5 minutes) that didn't raise any alarm. This graph describes better the representation of the data, for every device:
I need to use RNN class in python for alarm prediction. We define alarm when the temperature goes below the min limit or above the max limit.
After reading the official documentation from tensorflow here, i'm having troubles understanding how to set the input to the model. Should i normalise the data beforehand or something and if yes how?
Also reading the answers here didn't help me as well to have a clear view on how to transform my data into an acceptable format for the RNN model.
Any help on how the X and Y in model.fit should look like for my case?
If you see any other issue regarding this problem feel free to comment it.
PS. I have already setup python in docker with tensorflow, keras etc. in case this information helps.
You can begin with a snippet that you mention in the question.
Any help on how the X and Y in model.fit should look like for my case?
X should be a numpy matrix of shape [num samples, sequence length, D], where D is a number of values per timestamp. I suppose D=1 in your case, because you only pass temperature value.
y should be a vector of target values (as in the snippet). Either binary (alarm/not_alarm), or continuous (e.g. max temperature deviation). In the latter case you'd need to change sigmoid activation for something else.
Should i normalise the data beforehand
Yes, it's essential to preprocess your raw data. I see 2 crucial things to do here:
Normalise temperature values with min-max or standardization (wiki, sklearn preprocessing). Plus, I'd add a bit of smoothing.
Drop some fraction of last timestamps from all of the time-series to avoid information leak.
Finally, I'd say that this task is more complex than it seems to be. You might want to either find a good starter tutorial on time-series classification, or a course on machine learning in general. I believe you can find a better method than RNN.
Yes you should normalize your data. I would look at differencing by every day. Aka difference interval is 24hours / 5 minutes. You can also try and yearly difference but that depends on your choice in window size(remember RNNs dont do well with large windows). You may possibly want to use a log-transformation like the above user said but also this seems to be somewhat stationary so I could also see that not being needed.
For your model.fit, you are technically training the equivelant of a language model, where you predict the next output. SO your inputs will be the preciding x values and preceding normalized y values of whatever window size you choose, and your target value will be the normalized output at a given time step t. Just so you know a 1-D Conv Net is good for classification but good call on the RNN because of the temporal aspect of temperature spikes.
Once you have trained a model on the x values and normalized y values and can tell that it is actually learning (converging) then you can actually use the model.predict with the preciding x values and preciding normalized y values. Take the output and un-normalize it to get an actual temperature value or just keep the normalized value and feed it back into the model to get the time+2 prediction
I have a neural network with an input layer having 10 nodes, some hidden layers and an output layer with only 1 node. Then I put a pattern in the input layer, and after some processing, it outputs the value in the output neuron which is a number from 1 to 10. After the training this model is able to get the output , provided the input pattern.
Now, my question is, if it is possible to calculate the inverse model: This means, that I provide a number from output side, (i.e. using output side as input) and then getting the random pattern from those 10 input neurons (i.e. using input as output side).
I want to do this because I will first train a network on basis of difficulty of pattern (input is the pattern and output is difficulty to understand the pattern). Then I want to feed the network with a number so it creates the random patterns on basis of difficulty.
I hope I understood your problem correctly, so I will summarize it in my own words: You have a given model, and want to determine the input which yields a given output.
Supposed, that this is correct, there is at least one way I know of, how you can do this approximately. This way is very easy to implement, but might take a while to calculate a value - probably there are better ways to do this, but I am not sure. (I needed this technique some weeks ago in the topic of reinforcement learning, and did not find anything better, compared to this): Lets assume that your Model maps an input to an output . We now have to create a new model, which we will call : This model will later on calculate the inverse of the model , so that it gives you the input which yields a specific output. To construct we will create a new model, which consists of one plain Dense layer which has the same dimension m as the input. This layer will be connected to the input of the model now. Next, you make all weights of non-trainable (this is very important!).
Now we are setup to find an inverse value already: Assuming you want to find the input corresponding (corresponding means here: it creates the output, but is not unique) to the output y. You have to create a new input vector v which is the unity of . Then you create a input-output data pair consisting of (v, y). Now you use any optimizer you wish to let the input-output-trainingdata propagate through your network, until the error converges to zero. Once this has happend, you can calculate the real input, which gives the output y by doing this: Supposed, that the weights if the new input layer are called w, and the bias is b, the desired input u is u = w*1 + b (whereby 1 )
You might be asking for the reason why this equation holds, so let me try to answer it: You model will try to learn the weights of your new input layer, so that the unity as an input will create the given output. As only the newly added input layer is trainable, only this weights will be changed. Therefore, each weight in this vector will represent the corresponding component of the desired input vector. By using an optimizer and minimizing the l^2 distance between the wanted output and the output of our inverse-model , we will finally determine a set of weights, which will give you a good approximation for the input vector.
Data: When I have N rows of data like this: (x,y,z) where logically f(x,y)=z, that is z is dependent on x and y, like in my case (setting1, setting2 ,signal) . Different x's and y's can lead to the same z, but the z's wouldn't mean the same thing.
There are 30 unique setting1, 30 setting2 and 1 signal for each (setting1, setting2)-pairing, hence 900 signal values.
Data set: These [900,3] data points are considered 1 data set. I have many samples of these data sets.
I want to make a classification based on these data sets, but I need to flatten the data (make them all into one row). If I flatten it, I will duplicate all the setting values (setting1 and setting2) 30 times, i.e. I will have a row with 3x900 columns.
Question:
Is it correct to keep all the duplicate setting1,setting2 values in the data set? Or should I remove them and only include the unique values a single time?, i.e. have a row with 30 + 30 + 900 columns. I'm worried, that the logical dependency of the signal to the settings will be lost this way. Is this relevant? Or shouldn't I bother including the settings at all (e.g. due to correlations)?
If I understand correctly, you are training NN on a sample where each observation is [900,3].
You are flatning it and getting an input layer of 3*900.
Some of those values are a result of a function on others.
It is important which function, as if it is a liniar function, NN might not work:
From here:
"If inputs are linearly dependent then you are in effect introducing
the same variable as multiple inputs. By doing so you've introduced a
new problem for the network, finding the dependency so that the
duplicated inputs are treated as a single input and a single new
dimension in the data. For some dependencies, finding appropriate
weights for the duplicate inputs is not possible."
Also, if you add dependent variables you risk the NN being biased towards said variables.
E.g. If you are running LMS on [x1,x2,x3,average(x1,x2)] to predict y, you basically assign a higher weight to the x1 and x2 variables.
Unless you have a reason to believe that those weights should be higher, don't include their function.
I was not able to find any link to support, but my intuition is that you might want to decrease your input layer in addition to omitting the dependent values:
From professor A. Ng's ML Course I remember that the input should be the minimum amount of values that are 'reasonable' to make the prediction.
Reasonable is vague, but I understand it so: If you try to predict the price of a house include footage, area quality, distance from major hub, do not include average sun spot activity during the open home day even though you got that data.
I would remove the duplicates, I would also look for any other data that can be omitted, maybe run PCA over the full set of Nx[3,900].
i'm new to machine learning field.
Trying to classify 10 people with a their phone call logs.
The phone call logs look like this
UserId IsInboundCall Duration PhoneNumber(hashed)
1 false 23 1011112222
2 true 45 1033334444
Trained with this kind of 8700 logs with SVM from sklearn gives a result is accuracy 88%
I have a several question about this result and
what is a proper way to use some not ordinal data(ex. phone number)
I'm not sure using a hashed phone number as a feature but this multi class classifiers accuracy is not bad, is it just a coincidence?
How to use not oridnal data as a feature?
If this classifier have to classify more 1000 classes(more 1000 users), is SVM still work on that case?
Any advice is helpful for me. Thanks
1) Try the SVM without Phone number as a feature to get a sense of how much impact it has.
2) In order to avoid Ordinal Data you can either transform into a number or use a 1 of K approach. Say you added an Phone OS field with possible values {IOS, Android, Blackberry} you can represent this as a number 0,1,2 or as 3 features (1,0,0), (0,1,0), (0,0,1).
3) The SVM will still give good results as long as the data is approximately linearly separable. To achieve this you might need to add more features and map into a different feature space (an RBF kernel is a good start).