Need to transpose a pandas dataframe

Question

I have a Series that look like this:

      col1          id
 0      a           10
 1      b           20
 2      c           30
 3      b           10
 4           


        

Answer 1

You could use pd.crosstab

In [329]: pd.crosstab(df.id, df.col1)
Out[329]:
col1  a  b  c  d  e
id
10    1  1  0  1  0
20    0  1  0  0  0
30    1  0  1  0  0
40    0  0  0  0  1

Or, use pd.pivot_table

In [336]: df.pivot_table(index='id', columns='col1', aggfunc=len, fill_value=0)
Out[336]:
col1  a  b  c  d  e
id
10    1  1  0  1  0
20    0  1  0  0  0
30    1  0  1  0  0
40    0  0  0  0  1

Or, use groupby and unstack

In [339]: df.groupby(['id', 'col1']).size().unstack(fill_value=0)
Out[339]:
col1  a  b  c  d  e
id
10    1  1  0  1  0
20    0  1  0  0  0
30    1  0  1  0  0
40    0  0  0  0  1