Monday, September 23, 2013

Pandas panel = collection of tables/data frames aligned by index and column

Pandas panel provides a nice way to collect related data frames together while maintaining correspondence between the index and column values:


import pandas as pd, pylab

#Full dimensions of a slice of our panel
index = ['1','2','3','4'] #major_index
columns = ['a','b','c'] #minor_index

df = pd.DataFrame(pylab.randn(4,3),columns=columns,index=index) #A full slice of the panel
df2 = pd.DataFrame(pylab.randn(3,2),columns=['a','c'],index=['1','3','4']) #A partial slice
df3 = pd.DataFrame(pylab.randn(2,2),columns=['a','b'],index=['2','4']) #Another partial slice
df4 = pd.DataFrame(pylab.randn(2,2),columns=['d','e'],index=['5','6']) #Partial slice with a new column and index


pn = pd.Panel({'A': df})
pn['B'] = df2
pn['C'] = df3
pn['D'] = df4

for key in pn.items:
  print pn[key]

-> output

          a         b         c
1  0.243221 -0.142410  1.228757
2 -0.748140 -0.780719  0.644401
3  0.161369 -0.001034 -0.278070
4 -1.143613 -1.547082  0.025639
          a   b         c
1  1.165219 NaN  1.391501
2       NaN NaN       NaN
3 -1.484183 NaN  0.541619
4  0.810439 NaN -0.848142
          a         b   c
1       NaN       NaN NaN
2  1.310740  1.278829 NaN
3       NaN       NaN NaN
4  0.042748 -0.464065 NaN
    a   b   c
1 NaN NaN NaN
2 NaN NaN NaN
3 NaN NaN NaN
4 NaN NaN NaN

One thing to note is that Panel does not expand along the minor and major axes.

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