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pandas dataframe substracting columns: key error - metalray - Feb-23-2017
Hi Pandas Experts,
I got a dataframe that has a country and its GDP for the year 2015 up to 2006
newfour = newtwo[(newtwo['2015']-newtwo['2006'])]When I try to substract 2015 from 2006 and ingone the rest I read the error:
KeyError: '[ 4.80566748e+12 1.75626949e+12 1.73021626e+11 2.46702696e+11\n 2.30356251e+11 2.28139911e+11 3.52665152e+11 1.10131180e+12\n 1.53345695e+11 3.25560528e+11 -1.52854060e+11 4.99867550e+09\n nan 2.79311766e+11 4.74343726e+11] not in index'
It seems the GDP values are not an/in index but I wonder why that is required?
Why does a column need to be an index to be subtracted from another?
Many thanks for any explanations
RE: pandas dataframe substracting columns: key error - zivoni - Feb-23-2017
Well, I am not entirely sure what do you want to achieve, but if you just need to count difference of two columns of pandas' dataframe, then subtract them.
There is no need for your outer newtwo[...] selection , you are trying to use your computed differences as a keys and that wont work.
Output:In [1]: import pandas as pd
In [2]: newtwo = pd.DataFrame({'astate':['first', 'second'], 'gdp2010':[113.2, 341.1], 'gdp2015':[233.1, 417.1]})
In [3]: newtwo
Out[3]:
astate gdp2010 gdp2015
0 first 113.2 233.1
1 second 341.1 417.1
In [4]: newfour = newtwo['gdp2015'] - newtwo['gdp2010']
In [5]: newfour
Out[5]:
0 119.9
1 76.0
dtype: float64
In [6]: newtwo[(newtwo['gdp2010'] - newtwo['gdp2015'])] # same as newtwo[[-119.9, -76.0]] and that doesn't make sense ...
...
KeyError: '[-119.9 -76. ] not in index'RE: pandas dataframe substracting columns: key error - metalray - Feb-24-2017
(Feb-23-2017, 01:41 PM)zivoni Wrote: There is no need for your outer newtwo[...] selection , you are trying to use your computed differences as a keys and that wont work.
I see. That was it! I still get confused with this key and index thing.