MCA having problems with pandas CategoricalIndex

[omrihar]

It seems that, ironically, mca has some problems with handling a categorical index. I have such an index in my DataFrame which is created using pd.qcut(). When I run mca on this data I get an error:

AttributeError: 'Int64Index' object has no attribute '_is_dtype_compat'

I can work around this problem by using pd.to_numeric() on the offending column and then everything works. A minimal example that does not exactly yield the same error, but still does have a problem with the categorical index:

import numpy as np
import mca

a = np.random.normal(size=20)
aa = pd.qcut(a, 4, labels=list("1234"))
b = list(range(20))
c = list('abcdefghijklmnopqrst')
df = pd.DataFrame([aa,b,c], index=list(range(20)), columns=list('abc'))
# df.a = pd.to_numeric(df.a, downcast='integer')   # <- this fixes the problem
mymca = mca.mca(df, cols=['a','b'])

Running the above code yields the following error:

TypeError: cannot append a non-category item to a CategoricalIndex

Uncommenting the commented line fixes the problem. Hope this helps :-)

Cheers,
Omri

[esafak]

Thanks for reporting! I can reproduce the problem and am open to suggestions about how to solve it. It seems to be caused by a categorical first column, so checking for that and casting it to numeric should solve the problem. For example, these similar dataframes with re-assigned or re-ordered categorical columns don't have the same problem:

df.astype({'a':int, 'c':'category'})
df.assign(d=df.a).drop('a',1)

What do you think?