How to create bigrams of categorical column into separate columns?

Question

So I would like to take every row and split it into bigrams to be used as columns in order to encode the original string column.

I have a dataset like this one:

A
blue
red
black

I want my result to look like this:

A	bl	lu	ue	re	ed	la	ac	ck
blue	1	1	1	0	0	0	0	0
red	0	0	0	1	1	0	0	0
black	1	0	0	0	0	1	1	1

I have tried spliting up A but it does not split characters.

Asked By: revarein

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Source

Answer 1

Here’s a way to do:

# sample data
f = pd.DataFrame({'A': ['blue', 'red', 'black']})

def bigram(s, n=2):
    return [s[i:i+n] for i in range(0, len(s), 1) if len(s[i:i+2]) == n]

# using pandas 
f['bgm'] = f['A'].apply(bigram)
f = f.explode('bgm').reset_index(drop=True)
f = pd.crosstab(f['A'], f['bgm']).reset_index()
f.columns.name=None

print(f)

       A  ac  bl  ck  ed  la  lu  re  ue
0  black   1   1   1   0   1   0   0   0
1   blue   0   1   0   0   0   1   0   1
2    red   0   0   0   1   0   0   1   0

Answered By: YOLO

How to create bigrams of categorical column into separate columns?

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