python - Create adjacency matrix for two columns in pandas dataframe

Question

I have a dataframe of the form:

index  Name_A  Name_B
  0    Adam    Ben
  1    Chris   David
  2    Adam    Chris
  3    Ben     Chris

And I'd like to obtain the adjacency matrix for Name_A and Name_B, ie:

      Adam Ben Chris David
Adam   0    1    1     0
Ben    0    0    1     0
Chris  0    0    0     1
David  0    0    0     0

What is the most pythonic/scaleable way of tackling this?

EDIT: Also, I know that if the row Adam, Ben is in the dataset, then at some other point, Ben, Adam will also be in the dataset.

Answer 1

You can use crosstab and then reindex by union of column and index values:

df = pd.crosstab(df.Name_A, df.Name_B)
print (df)
Name_B  Ben  Chris  David
Name_A                   
Adam      1      1      0
Ben       0      1      0
Chris     0      0      1

df = pd.crosstab(df.Name_A, df.Name_B)
idx = df.columns.union(df.index)
df = df.reindex(index = idx, columns=idx, fill_value=0)
print (df)
       Adam  Ben  Chris  David
Adam      0    1      1      0
Ben       0    0      1      0
Chris     0    0      0      1
David     0    0      0      0