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pythonpandasdataframeindexingargmax

Find row-index of highest value in given column of dataframe


I want to order a DataFrame by increasing value of column number, and get the indexof that highest value. (Here it's the second row, so the result should be 'BCD':

    number L-word ID
ABC 1      Lord   ABC works
BCD 25     Land   BCD works
CDE 3      Loft   CDE works

(Is there a solution that is not even remotely as weird as the following hack of mine? I worked around this by adding another column with the same name, just so that I understand how that could work in general) So here is the code I came up with:

numbers_ordered = df.sort_values(['number'], ascending = False, na_position='last')
    df = numbers_ordered[:1]
    a = dict(df.head())
    b = a['ID']
    b = str(b)
    c = b[:2]

This seems to be incredibly awkward and there should be an easy option to do this, however I cannot find it in the documentation of pandas as well as the www. I had the idea of changing the index (something like df = df.reset_index()) and then turning the old index into a new column but that would still not be the ultimate solution since I think there should be an option to just "extract" the index of the top hit of my df?


Solution

  • Try df['number'].argmax()

    import pandas
    import numpy as np
    df = pandas.DataFrame(np.random.randn(10,3),columns=['Col1','Col2','Col3'])
    print df
    print df['Col1'].argmax()
    

    output

                    Col1      Col2      Col3
    0  0.583251 -0.014694  1.516529
    1  0.274758  0.438513  0.994992
    2  0.601611  1.753035  0.864451
    3 -0.971775 -1.461290  0.121570
    4  2.239460 -1.099298 -1.953045
    5  2.314444  0.215336  0.470668
    6 -0.138696  0.422923 -0.624436
    7  0.602329 -0.015627  0.023715
    8  0.594784  0.739058  1.094646
    9 -0.104579  0.557339  1.977929
    
    5