Hashtag-based Tweet similarity - machine-learning

I have a big dataset consisting of tweets including hashtags and I want to build a hashtag-based similarity engine to get the most similar tweets given a set of hashtags.
In the end I would like to have some kind of "hashtag to vector embedding" model (should work like a language embedding model) which outputs a comparable vector, based on a set of input hashtags.
One idea would be to fit a TF IDF Vectorizer and then take the cosine similarity between a query vector and the tweet vectors.
However, there come some problems with this solution (very big vectors, out of dictionary vectors of new tweets,...) and I feel like there are some better solutions for the problem, do you have any other solutions/pretrained model for the problem which you can recommend or I should try?

Related

Storing TF-IDF values in an inverted index

I'm creating a search engine to search a list of roughly 20k English phrases, each one being a few words long.
I've looked into ways to create the search engine, and currently I am using a TfidfVectorizer from sklearn and Cosine Similarity to compute the ranking scores.
From what I understand in information retrieval you have retrieval and ranking phases, however I'm confused how you could use a data structure like an inverted index to speed up the search before using TfidfVectorizer? It seems like TfidfVectorizer creates a term-document matrix which is different to an index. Could you just store TF and IDF values in an inverted index and use cosine similarity at run time? Ideally I want autocomplete of phrases so I need to store edge ngrams as well, and a boolean model isn't useful here.

Mutli-Class Text Classifcation (using TFIDF and SVM). How to implement a scenario where one feedback may belong to more than one class?

I have a file of raw feedbacks that needs to be labeled(categorized) and then work as the training input for SVM Classifier(or any classifier for that matter).
But the catch is, I'm not assigning whole feedback to a certain category. One feedback may belong to more than one category based on the topics it talks about (noun n-grams are extracted). So, I'm labeling the topics(terms) not the feedbacks(documents). And so, I've extracted the n-grams using TFIDF while saving their features so i could train my model on. The problem with that is, using tfidf, it returns a document-term matrix that's train_x, but on the other side, I've got train_y; The labels that are assigned to each n-gram (not the whole document). So, I've ended up with a document to frequency matrix that contains x number of rows(no of documents) against a label of y number of n-grams(no of unique topics extracted).
Below is a sample of what the data look like. Blue is the n-grams(extracted by TFIDF) while the red is the labels/categories (calculated for each n-gram with a function I've manually made).
Instead of putting code, this is my strategy in implementing my concept:
The problem lies in that part where TFIDF producesx_train = tf.Transform(feedbacks), which is a document-term matrix and it doesn't make sense for it to be an input for the classifier against y_train, which is the labels for the terms and not the documents. I've tried to transpose the matrix, it gave me an error. I've tried to input 1-D array that holds only feature values for the terms directly, which also gave me an error because the classifier expects from X to be in a (sample, feature) format. I'm using Sklearn's version of SVM and TfidfVectorizer.
Simply, I want to be able to use SVM classifier on a list of terms (n-grams) against a list of labels to train the model and then test new data (after cleaning and extracting its n-grams) for SVM to predict its labels.
The solution might be a very technical thing like using another classifier that expects a different format or not using TFIDF since it's document focused (referenced) or even broader, a whole change of approach and concept (if it's wrong).
I'd very much appreciate it if someone could help.

Is it possible to fine-tune BERT to do retweet prediction?

I want to build a classifier that predicts if user i will retweet tweet j.
The dataset is huge, it contains 160 million tweets. Each tweet comes along with some metadata(e.g. does the retweeter follow the user of the tweet).
the text tokens for a single tweet is an ordered list of BERT ids. To get the embedding of the tweet, you just use the ids (So it is not text)
Is it possible to fine-tune BERT to do the prediction? if yes, what do courses/sources do you recommend to learn how to fine-tune? (I'm a beginner)
I should add that the prediction should be a probability.
If it's not possible, I'm thinking of converting the embeddings back to text then using some arbitrary classifier that I'm going to train.
You can fine-tune BERT, and you can use BERT to do retweet prediction, but you need more architecture in order to predict if user i will retweet tweet j.
Here is an architecture off the top of my head.
At a high level:
Create a dense vector representation (embedding) of user i (perhaps containing something about the user's interests, such as sports).
Create an embedding of tweet j.
Create an embedding of the combination of the first two embeddings together, such as with concatenation or hadamard product.
Feed this embedding through a NN that performs binary classification to predict retweet or non-retweet.
Let's break this architecture down by item.
To create an embedding of user i, you will need to create some kind of neural network that accepts whatever features you have about the user and produces a dense vector. This part is the most difficult component of the architecture. This area is not in my wheelhouse, but a quick google search for "user interest embedding" brings up this research paper on an algorithm called StarSpace. It suggests that it can "obtain highly informative user embeddings according to user behaviors", which is what you want.
To create an embedding of tweet j, you can use any type of neural network that takes tokens and produces a vector. Research prior to 2018 would have suggested using an LSTM or a CNN to produce the vector. However, BERT (as you mentioned in your post) is the current state-of-the-art. It takes in text (or text indices) and produces a vector for each token; one of those tokens should have been the prepended [CLS] token, which commonly is taken to be the representation of the whole sentence. This article provides a conceptual overview of the process. It is in this part of the architecture that you can fine-tune BERT. This webpage provides concrete code using PyTorch and the Huggingface implementation of BERT to do this step (I've gone through the steps and can vouch for it). In the future, you'll want to google for "BERT single sentence classification".
To create an embedding representing the combination of user i and tweet j, you can do one of many things. You can simply concatenate them together into one vector; so if user i is an M-dimensional vector and tweet j is an N-dimensional vector, then the concatenation produces an (M+N)-dimensional vector. An alternative approach is to compute the hadamard product (element-wise multiplication); in this case, both vectors must have the same dimension.
To make the final classification of retweet or not-retweet, build a simple NN that takes the combination vector and produces a single value. Here, since you are doing binary classification, a NN with a logistic (sigmoid) function would be appropriate. You can interpret the output as the probability of retweeting, so a value above 0.5 would be to retweet. See this webpage for basic details on building a NN for binary classification.
In order to get this whole system to work, you need to train it all together end-to-end. That is, you have to get all the pieces hooked up first and train it rather than training the components separately.
Your input dataset would look something like this:
user tweet retweet?
---- ----- --------
20 years old, likes sports Great game Y
30 years old, photographer Teen movie was good N
If you want an easier route where there is no user personalization, then just leave out the components that create an embedding of user i. You can use BERT to build a model to determine if the tweet is retweeted without regard to user. You can again follow the links I mentioned above.
There is already an answer on this in Data Science SE, which explains why BERT cannot be used for prediction. Here is the gist:
BERT can't be used for next word prediction, at least not with the current state of the research on masked language modeling.
BERT is trained on a masked language modeling task and therefore you cannot "predict the next word". You can only mask a word and ask BERT to predict it given the rest of the sentence (both to the left and to the right of the masked word).
But as I understand from your case that you want to do 'classification' then BERT is fully equipped to do that. Please refer to the link I have posted below. This will help you to classify the tweets according to its topic so you may then view them in your Leisure time.

Fuzzy matching sentences to stanzas

I have lyrics from srt subtitle files. If I want to match them to stanzas from another lyrics website, what is the best approach to this?
My approach has been taking tf-idf vector each lyric line and trying to fuzzy match to the staza, using starting and end time of the lyric line as a clue to whether the line might belong to the previous stanzas, next stanzas, or belong to a stanzas of it's own.
I've also tried dynamic programming, but with less success. Due to the high variance in the structure of the lyrics and the stanza, sometimes the results come out completely shifted or messed up, especially if there are repeated chorus.
If there is a Recurrent Neural Networks or other Machine Learning algorithm, is there an existing approach to such problem?
I suggest using Doc2Vec or Word2Vec methods, basically you train a NN with some corpus, the NN will generate a vector for each word/document, those vectors will have similarity based on the similarty of words in the real world (corpus)
so vector of love and care will be very similar, those vectors hold some other cool properties like if yo subtract or add them you can get a word that posses some meaning of the substation or addition induce
once you will get the vector of words or docs you can check similarity between vectors with various methods, commonly used is the cosine similarity
this method mixed with tf-idf to generate weights for best results
usage is very easy, for example
from gensim.models import Word2Vec
from nltk.corpus import brown
b = Word2Vec(brown.sents())
print b.most_similar('money', topn=5)
output
[(u'care', 0.9145717024803162), (u'chance', 0.9034961462020874), (u'job', 0.8980690240859985), (u'trouble', 0.8751360774040222), (u'everything', 0.873866856098175)]
I suggest to take a look at gensim

Am I using word-embeddings correctly?

Core question : Right way(s) of using word-embeddings to represent text ?
I am building sentiment classification application for tweets. Classify tweets as - negative, neutral and positive.
I am doing this using Keras on top of theano and using word-embeddings (google's word2vec or Stanfords GloVe).
To represent tweet text I have done as follows:
used a pre-trained model (such as word2vec-twitter model) [M] to map words to their embeddings.
Use the words in the text to query M to get corresponding vectors. So if the tweet (T) is "Hello world" and M gives vectors V1 and V2 for the words 'Hello' and 'World'.
The tweet T can then be represented (V) as either V1+V2 (add vectors) or V1V2 (concatinate vectors)[These are 2 different strategies] [Concatenation means juxtaposition, so if V1, V2 are d-dimension vectors, in my example T is 2d dimension vector]
Then, the tweet T is represented by vector V.
If I follow the above, then My Dataset is nothing but vectors (which are sum or concatenation of word vectors depending on which strategy I use).
I am training a deepnet such as FFN, LSTM on this dataset. But my results arent coming out to be great.
Is this the right way to use word-embeddings to represent text ? What are the other better ways ?
Your feedback/critique will be of immense help.
I think that, for your purpose, it is better to think about another way of composing those vectors. The literature on word embeddings contains examples of criticisms to these kinds of composition (I will edit the answer with the correct references as soon as I find them).
I would suggest you to consider also other possible approaches, for instance:
Using the single word vectors as input to your net (I do not know your architecture, but the LSTM is recurrent so it can deal with sequences of words).
Using a full paragraph embedding (i.e. https://cs.stanford.edu/~quocle/paragraph_vector.pdf)
Summing them doesn't make any sense to be honest, because on summing them you get another vector which i don't think represents the semantics of "Hello World" or may be it does but it won't surely hold true for longer sentences in general
Instead it would be better to feed them as sequence as in that way it at least preserves sequence in meaningful way which seems to fit more to your problem.
e.g A hates apple Vs Apple hates A this difference would be captured when you feed them as sequence into RNN but their summation will be same.
I hope you get my point!

Resources