pandas dataframe sort on column raises keyerror on index

Question

I have the following dataframe, df:

   peaklatency        snr
0        52.99        0.0
1        54.15  62.000000
2        54.12  82.000000
3        54.64  52.000000
4        54.57  42.000000
5        54.13  72.000000

I'm attempting to sort this by snr:

df.sort_values(df.snr)

but this raises

_convert_to_indexer(self, obj, axis, is_setter)
   1208                 mask = check == -1
   1209                 if mask.any():
-> 1210                     raise KeyError('%s not in index' % objarr[mask])
   1211 
   1212                 return _values_from_object(indexer)

KeyError: '[ inf  62.  82.  52.  42.  72.] not in index'

I am not explicitly setting an index on this DataFrame, it's coming from a list comprehension:

    import pandas as pd
    d = []
    for run in runs:
        d.append({            
            'snr': run.periphery.snr.snr,
            'peaklatency': (run.brainstem.wave5.wave5.argmax() / 100e3) * 1e3
        })
    df = pd.DataFrame(d)

chrisb · Accepted Answer · 2016-08-07 02:54:23Z

8

The by keyword to sort_values expects column names, not the actual Series itself. So, you'd want:

In [23]: df.sort_values('snr')
Out[23]: 
   peaklatency   snr
0        52.99   0.0
4        54.57  42.0
3        54.64  52.0
1        54.15  62.0
5        54.13  72.0
2        54.12  82.0

answered Aug 7, 2016 at 2:54

chrisb

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2 Comments

duldi Over a year ago

what if the column does not have a name?

Kenan Over a year ago

how can your columns be nameless?

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