count_nested

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count_nested#

count_nested(df, nested, by=None, join=True) → NestedFrame[source]#

Counts the number of rows of a nested dataframe.

Parameters:

  • df (NestedFrame) – A NestedFrame that contains the desired nested series to count.

  • nested ('str') – The label of the nested series to count.

  • by ('str', optional) – Specifies a column within nested to count by, returning a count for each unique value in by.

  • join (bool, optional) – Join the output count columns to df and return df, otherwise just return a NestedFrame containing only the count columns.

Return type:

NestedFrame

Examples

>>> import pandas as pd
>>> # Show all columns
>>> pd.set_option("display.width", 200)
>>> pd.set_option("display.max_columns", None)
>>> from nested_pandas.datasets.generation import generate_data
>>> nf = generate_data(5, 10, seed=1)

>>> from nested_pandas.utils import count_nested
>>> count_nested(nf, "nested")
          a         b                                             nested  n_nested
0  0.417022  0.184677  [{t: 8.38389, flux: 10.233443, flux_error: 1.0...        10
1  0.720324  0.372520  [{t: 13.70439, flux: 41.405599, flux_error: 1....        10
2  0.000114  0.691121  [{t: 4.089045, flux: 69.440016, flux_error: 1....        10
3  0.302333  0.793535  [{t: 17.562349, flux: 41.417927, flux_error: 1...        10
4  0.146756  1.077633  [{t: 0.547752, flux: 4.995346, flux_error: 1.0...        10

count_nested also allows counting by a given subcolumn, for example we can count by “band” label:

>>> # join=False, allows the result to be kept separate from the original nf
>>> count_nested(nf, "nested", by="band", join=False)
   n_nested_g  n_nested_r
0           8           2
1           5           5
2           5           5
3           6           4
4           6           4
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