plydata.one_table_verbs.define¶

class plydata.one_table_verbs.define(*args, **kwargs)[source]¶

Add column to DataFrame

Parameters

datadataframe, optional: Useful when not using the >> operator.
argsstrs, tuples, optional: Expressions or (name, expression) pairs. This should be used when the name is not a valid python variable name. The expression should be of type str or an interable with the same number of elements as the dataframe.
kwargsdict, optional: {name: expression} pairs.

Notes

If plydata.options.modify_input_data is True, define will modify the original dataframe.

Examples

>>> import pandas as pd
>>> df = pd.DataFrame({'x': [1, 2, 3]})
>>> df >> define(x_sq='x**2')
   x  x_sq
0  1     1
1  2     4
2  3     9
>>> df >> define(('x*2', 'x*2'), ('x*3', 'x*3'), x_cubed='x**3')
   x  x*2  x*3  x_cubed
0  1    2    3        1
1  2    4    6        8
2  3    6    9       27
>>> df >> define('x*4')
   x  x*4
0  1    4
1  2    8
2  3   12