In natural language processing, *vectors* are very important! They contain numerical information that indicates the magnitude of the pieces of data being represented.

The dimension, or size, of a vector can be manipulated to allow for more data to be stored in the vector. Above, three one-dimensional vectors are shown.

In Python, you can represent a vector with a *NumPy* array. The following creates a vector of **even** numbers from 2 to 10.

```
even_nums = np.array([2,4,6,8,10])
```

*Word embeddings* are key to natural language processing. Each is a real number vector representation of a specific word. Contextual information about that word is encoded within the vector numbers.

A basic English word embedding model can be loaded in Python using the `spaCy`

library. This allows access to embeddings for English words.

nlp = spacy.load('en')

Call the model with the desired word as an argument and access the `.vector`

attribute:

nlp('peace').vector

The result would be:

```
[5.2907305, -4.20267, 1.6989858, -1.422668, -1.500128, ...]
```

Measuring distances between word embedding vectors allows us to look at the similarities and differences between words. This type of distance can be calculated using either *Manhattan*, *Euclidean* or *Cosine distance*.

With large-dimensional vectors, **Cosine distance** is preferred because Manhattan and Euclidean distances can become too large. Cosine produces **much smaller** values; it measures the angle between two vectors, whereas the other two calculate distances between vector points.

The Python library *SciPy* contains functions to calculate each easily given two vectors `a`

and `b`

.

from scipy.spatial.distance import cityblock, euclidean, cosinemanhattan_d = cityblock(a,b) # 129.62euclidean_d = euclidean(a,b) # 16.45cosine_d = cosine(a,b) # 0.25

Words used in similar contexts have similar word embeddings, meaning that they are mapped to similar areas in the vector space.

Words in similar contexts have a **small** *cosine distance*, while words in different contexts have a **large** *cosine distance*.

The vectors for “cat” and “scrabble” point to similar areas of the vector space, and “antidisestablishmentarianism” points to a very different area.

“cat” and “scrabble” would have a **small** cosine distance, and “cat” and “antidisestablishmentarianism” would have a **large** one.

To compare word embedding vectors, vector values need to first be appropriately created! *Word2vec* is a statistical learning algorithm that creates embeddings using written text (a *corpus*). There are two different architectures of the corpus it can use:

*Continuous Bag of Words*: the algorithm goes through each word in the training corpus, in order, and predicts the word at each position based on applying bag-of-words to surrounding words. The order of the words does**not**matter!*Continuous Skip-Grams*: Look at sequences of words that are separated by some specified distance, as opposed to the common practice of looking at groups of n-consecutive words in a text (*n-grams*). The order of context**is**taken into consideration!

Instead of using pre-trained word embeddings from *spaCy*, you can create your own unique ones! The Python library `gensim`

allows a *word2vec* model to be trained on any corpus of text. These embeddings can be any specified dimension and are unique contextual embeddings to that corpus of text.

`corpus`

: A list of lists. Each inner list is a document in the corpus, each element in the inner lists is a word token`size`

: The dimensions of the embeddings.- Don’t worry about the other arguments.

Model attributes:

`.wv.vocab.items()`

– vocabulary of the model`.most_similar("cat", topn=10)`

– 10 most similar words to “cat”`.doesnt_match(["mouse", "cat", "europe"])`

– identify the word**least**like others

import gensimmodel = gensim.models.Word2Vec(corpus, size=100, window=5, min_count=1, workers=2, sg=1)

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