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pythonpandasnumpydataframebinning

Binning a column with pandas


I have a data frame column with numeric values:

df['percentage'].head()
46.5
44.2
100.0
42.12

I want to see the column as bin counts:

bins = [0, 1, 5, 10, 25, 50, 100]

How can I get the result as bins with their value counts?

[0, 1] bin amount
[1, 5] etc
[5, 10] etc
...

Solution

  • You can use pandas.cut:

    bins = [0, 1, 5, 10, 25, 50, 100]
    df['binned'] = pd.cut(df['percentage'], bins)
    print (df)
       percentage     binned
    0       46.50   (25, 50]
    1       44.20   (25, 50]
    2      100.00  (50, 100]
    3       42.12   (25, 50]
    

    bins = [0, 1, 5, 10, 25, 50, 100]
    labels = [1,2,3,4,5,6]
    df['binned'] = pd.cut(df['percentage'], bins=bins, labels=labels)
    print (df)
       percentage binned
    0       46.50      5
    1       44.20      5
    2      100.00      6
    3       42.12      5
    

    Or numpy.searchsorted:

    bins = [0, 1, 5, 10, 25, 50, 100]
    df['binned'] = np.searchsorted(bins, df['percentage'].values)
    print (df)
       percentage  binned
    0       46.50       5
    1       44.20       5
    2      100.00       6
    3       42.12       5
    

    ...and then value_counts or groupby and aggregate size:

    s = pd.cut(df['percentage'], bins=bins).value_counts()
    print (s)
    (25, 50]     3
    (50, 100]    1
    (10, 25]     0
    (5, 10]      0
    (1, 5]       0
    (0, 1]       0
    Name: percentage, dtype: int64
    

    s = df.groupby(pd.cut(df['percentage'], bins=bins)).size()
    print (s)
    percentage
    (0, 1]       0
    (1, 5]       0
    (5, 10]      0
    (10, 25]     0
    (25, 50]     3
    (50, 100]    1
    dtype: int64
    

    By default cut returns categorical.

    Series methods like Series.value_counts() will use all categories, even if some categories are not present in the data, operations in categorical.