word2vec | Python Word2Vec example | Machine Learning library

The problem is that the referenced repository trained a model on an incredibly old version of GenSim, which makes it incompatible with current versions.

You can potentially check whether the lifecycle meta data gives you any indication on the actual version, and then try to update your model from there. The documentation also gives some tips for upgrading your older trained models, but even those are relatively weak and point mostly to re-training. Similarly, even migrating from GenSim 3.X to 4.X is not referencing direct upgrade methods, but could give you ideas on what parameters to look out for specifically.

My suggestion would be to try loading it with any of the previous 3.X versions, and see if you have more success loading it there.

First & foremost, beyond a certain size of data, & especially when working with raw text or tokenized text, you probably don't want to be using Pandas dataframes for every interim result.

They add extra overhead & complication that isn't fully 'Pythonic'. This is particularly the case for:

• Python list objects where each word is a separate string: once you've tokenized raw strings into this format, as for example to feed such texts to Gensim's Word2Vec model, trying to put those into Pandas just leads to confusing list-representation issues (as with your columns where the same text might be shown as either ['yessir', 'shit', 'is', 'real'] – which is a true Python list literal – or [yessir, shit, is, real] – which is some other mess likely to break if any tokens have challenging characters).
• the raw word-vectors (or later, text-vectors): these are more compact & natural/efficient to work with in raw Numpy arrays than Dataframes

So, by all means, if Pandas helps for loading or other non-text fields, use it there. But then use more fundamntal Python or Numpy datatypes for tokenized text & vectors - perhaps using some field (like a unique ID) in your Dataframe to correlate the two.

Especially for large text corpuses, it's more typical to get away from CSV and instead use large text files, with one text per newline-separated line, and any each line being pre-tokenized so that spaces can be fully trusted as token-separated.

That is: even if your initial text data has more complicated punctuation-sensative tokenization, or other preprocessing that combines/changes/splits other tokens, try to do that just once (especially if it involves costly regexes), writing the results to a single simple text file which then fits the simple rules: read one text per line, split each line only by spaces.

Lots of algorithms, like Gensim's Word2Vec or FastText, can either stream such files directly or via very low-overhead iterable-wrappers - so the text is never completely in memory, only read as needed, repeatedly, for multiple training iterations.

For more details on this efficient way to work with large bodies of text, see this artice: https://rare-technologies.com/data-streaming-in-python-generators-iterators-iterables/

The full source code is available:

https://github.com/facebookresearch/fastText

So, you can make any changes or extensions you can imagine - if you're comfortable reading & modifying its C++ source code. Nothing is hidden or inaccessible.

Note that both FastText, and its supervised classification mode, are chiefly conventions for training a shallow neural-network. It may not be helpful to think of it as a "pipeline" like in the architecture of other classifier libraries - as none of the internal interfaces use that sort of language or modular layout.

Specifically, if you get the gist of word2vec training, FastText classifier mode really just replaces attempted-predictions of neighboring (in-context-window) vocabulary words, with attempted-predictions of known labels instead.

For the sake of understanding FastText's relationship to other techniques, and potential aspects for further extension, I think it's useful to also review:

• this skeptical blog post comparing FastText to the much-earlier 'vowpal wabbit' tool: "Fast & easy baseline text categorization with vw"
• Facebook's far-less discussed extension of such vector-training for more generic categorical or numerical tasks, "StarSpace"

The line in the tutorial:

You can call the function on one skip-grams's target word and pass the context word as a true class to exclude it from being sampled

That's misleading.

What does true_classes mean in this function?

Function returns true_expected_count which is defined in this line of the source code..

true_classes seems only used to calculate true_expected_count. So this function does not exclude negative classes. Every label has a probability to get sampled.

I copy an example code that can be experimented on (in case something happens to the link), taken from this GitHub issue:

A vector size of 1000 dimensions is very uncommon, and would require massive amounts of data to train. For example, the famous GoogleNews vectors were for 3 million words, trained on something like 100 billion corpus words - and still only 300 dimensions. Your STEMMED_TOKENS may not be enough data to justify 100-dimensional vectors, much less 300 or 1000.

A choice of min_count=1 is a bad idea. This algorithm can't learn anything valuable from words that only appear a few times. Typically people get better results by discarding rare words entirely, as the default min_count=5 will do. (If you have a lot of data, you're likely to increase this value to discard even more words.)

Are you examining the model's size or word-to-word results at all to ensure it's doing what you expect? Despite your colum being named STEMMED_TOKENS, I don't see any actual splitting-into-tokens, and the Word2Vec class expects each text to be a list-of-strings, not a string.

Finally, without seeing all your other choices for feeding word-vector-enriched data to your other classification steps, it is possible (likely even) that there are other errors there.

Given that a binary-classification model can always get at least 50% accuracy by simply classifying every example with whichever class is more common, any accuracy result less than 50% should immediately cause suspicions of major problems in your process like:

• misalignment of examples & labels
• insufficient/unrepresentative training data
• some steps not running at all due to data-prep or invocation errors

Averaging is most typical, when someone is looking for a super-simple way to turn a bag-of-words into a single fixed-length vector.

You could try a simple sum, as well.

But note that the key difference between the sum and average is that the average divides by the number of input vectors. Thus they both result in a vector that's pointing in the exact same 'direction', just of different magnitude. And, the most-often-used way of comparing such vectors, cosine-similarity, is oblivious to magnitudes. So for a lot of cosine-similarity-based ways of later comparing the vectors, sum-vs-average will give identical results.

On the other hand, if you're comparing the vectors in other ways, like via euclidean-distances, or feeding them into other classifiers, sum-vs-average could make a difference.

Similarly, some might try unit-length-normalizing all vectors before use in any comparisons. After such a pre-use normalization, then:

• euclidean-distance (smallest to largest) & cosine-similarity (largest-to-smallest) will generate identical lists of nearest-neighbors
• average-vs-sum will result in different ending directions - as the unit-normalization will have upped some vectors' magnitudes, and lowered others, changing their relative contributions to the average.

What should you do? There's no universally right answer - depending on your dataset & goals, & the ways your downstream steps use the vectors, different choices might offer slight advantages in whatever final quality/desirability evaluation you perform. So it's common to try a few different permutations, along with varying other parameters.

Separately:

• The GoogleNews vectors were trained on news articles back around 2013; their word senses thus may not be optimal for an image-labeling task. If you have enough of your own data, or can collect it, training your own word-vectors might result in better results. (Both the use of domain-specific data, & the ability to tune training parameters based on your own evaluations, could offer benefits - especially when your domain is unique, or the tokens aren't typical natural-language sentences.)
• There are other ways to create a single summary vector for a run-of-tokens, not just arithmatical-combo-of-word-vectors. One that's a small variation on the word2vec algorithm often goes by the name Doc2Vec (or 'Paragraph Vector') - it may also be worth exploring.
• There are also ways to compare bags-of-tokens, leveraging word-vectors, that don't collapse the bag-of-tokens to a single fixed-length vector 1st - and while they're more expensive to calculate, sometimes offer better pairwise similarity/distance results than simple cosine-similarity. One such alternate comparison is called "Word Mover's Distance" - at some point,, you may want to try that as well.

When you perform a new call to .train(), it only trains on the new data. So only words in the new data can possibly be updated.

And to the extent that the new data may be smaller, and more idiosyncratic in its word usages, any words in the new data will be trained to only be consistent with other words being trained in the new data. (Depending on the size of the new data, and the training parameters chosen like alpha & epochs, they might be pulled via the new examples arbitrarily far from their old locations - and thus start to lose comparability to words that were trained earlier.)

(Note also that when providing an different corpus that the original, you shouldn't use a parameter like total_examples=model.corpus_count, reusing model.corpus_count, a value cahced in the model from the earlier data. Rather, parameters should describe the current batch of data.)

Frankly, I'm not a fan of this feature. It's possible it could be useful to advanced users. But most people drawn to it are likely misuing it, expecting any number of tiny incremental updates to constantly expand & improve the model - when there's no good support for the idea that will reliably happen with naive use.

In fact, there's reasons to doubt such updates are generally a good idea. There's even an established term for the risk that incremental updates to a neural-network wreck its prior performance: catastrophic forgetting.

The straightforward & best-grounded approach to updating word-vectors for new expanded data is to re-train from scratch, so all words are on equal footing, and go through the same interleaved training, on the same unified optimization (SGD) schedule. (The new new vectors at the end of such a process will not be in a compatible coordinate space, but should be equivalently useful, or better if the data is now bigger and better.)

As of Gensim 4.0 & higher, the Word2Vec model doesn't support subscripted-indexed access (the ['...']') to individual words. (Previous versions would display a deprecation warning, Method will be removed in 4.0.0, use self.wv.getitem() instead`, for such uses.)

So, when you want to access a specific word, do it via the Word2Vec model's .wv property, which holds just the word-vectors, instead. So, your (unshown) word_vector() function should have its line highlighted in the error stack changed to:

I've not tried the nonsense parameter epochs=0, but it might behave as you expect. (Have you tried it and seen otherwise?)

However, if your real goal is to be able to tamper with the model after initialization, but before training, the usual way to do that is to not supply any corpus when constructing the model instance, and instead manually do the two followup steps, .build_vocab() & .train(), in your own code - inserting extra steps between the two. (For even finer-grained control, you can examine the source of .build_vocab() & its helper methods, and simply ensure you do all those necessary things, with your own extra steps interleaved.)

The "word vectors" in the .wv property of type KeyedVectors are essentially the "input projection layer" of the model: the data which converts a single word into a vector_size-dimensional dense embedding. (You can think of the keys – word token strings – as being somewhat like a one-hot word-encoding.)

So, assigning into that structure only changes that "input projection vector", which is the "word vector" usually collected from the model. If you need to tamper with the hidden-to-output weights, you need to look at the model's .syn1neg (or .syn1 for HS mode) property.