:mod:`dfply.window_functions`
=============================

.. py:module:: dfply.window_functions







Module Contents
---------------






.. function:: lead(series, i=1)

   
   Returns a series shifted forward by a value. `NaN` values will be filled
   in the end.

   Same as a call to `series.shift(i)`

   Args:
       series: column to shift forward.
       i (int): number of positions to shift forward.

   









.. function:: lag(series, i=1)

   
   Returns a series shifted backwards by a value. `NaN` values will be filled
   in the beginning.

   Same as a call to `series.shift(-i)`

   Args:
       series: column to shift backward.
       i (int): number of positions to shift backward.

   









.. function:: between(series, a, b, inclusive=False)

   
   Returns a boolean series specifying whether rows of the input series
   are between values `a` and `b`.

   Args:
       series: column to compare, typically symbolic.
       a: value series must be greater than (or equal to if `inclusive=True`)
           for the output series to be `True` at that position.
       b: value series must be less than (or equal to if `inclusive=True`) for
           the output series to be `True` at that position.

   Kwargs:
       inclusive (bool): If `True`, comparison is done with `>=` and `<=`.
           If `False` (the default), comparison uses `>` and `<`.

   









.. function:: dense_rank(series, ascending=True)

   
   Equivalent to `series.rank(method='dense', ascending=ascending)`.

   Args:
       series: column to rank.

   Kwargs:
       ascending (bool): whether to rank in ascending order (default is `True`).

   









.. function:: min_rank(series, ascending=True)

   
   Equivalent to `series.rank(method='min', ascending=ascending)`.

   Args:
       series: column to rank.

   Kwargs:
       ascending (bool): whether to rank in ascending order (default is `True`).

   









.. function:: cumsum(series)

   
   Calculates cumulative sum of values. Equivalent to `series.cumsum()`.

   Args:
       series: column to compute cumulative sum for.

   









.. function:: cummean(series)

   
   Calculates cumulative mean of values. Equivalent to
   `series.expanding().mean()`.

   Args:
       series: column to compute cumulative mean for.

   









.. function:: cummax(series)

   
   Calculates cumulative maximum of values. Equivalent to
   `series.expanding().max()`.

   Args:
       series: column to compute cumulative maximum for.

   









.. function:: cummin(series)

   
   Calculates cumulative minimum of values. Equivalent to
   `series.expanding().min()`.

   Args:
       series: column to compute cumulative minimum for.

   









.. function:: cumprod(series)

   
   Calculates cumulative product of values. Equivalent to
   `series.cumprod()`.

   Args:
       series: column to compute cumulative product for.

   









.. function:: cumany(series)

   
   Calculates cumulative any of values. Equivalent to
   `series.expanding().apply(np.any).astype(bool)`.

   Args:
       series: column to compute cumulative any for.

   









.. function:: cumall(series)

   
   Calculates cumulative all of values. Equivalent to
   `series.expanding().apply(np.all).astype(bool)`.

   Args:
       series: column to compute cumulative all for.

   









.. function:: percent_rank(series, ascending=True)

   









.. function:: row_number(series, ascending=True)

   
   Returns row number based on column rank
   Equivalent to `series.rank(method='first', ascending=ascending)`.

   Args:
       series: column to rank.

   Kwargs:
       ascending (bool): whether to rank in ascending order (default is `True`).

   Usage:
   diamonds >> head() >> mutate(rn=row_number(X.x))

      carat      cut color clarity  depth  table  price     x     y     z   rn
   0   0.23    Ideal     E     SI2   61.5   55.0    326  3.95  3.98  2.43  2.0
   1   0.21  Premium     E     SI1   59.8   61.0    326  3.89  3.84  2.31  1.0
   2   0.23     Good     E     VS1   56.9   65.0    327  4.05  4.07  2.31  3.0
   3   0.29  Premium     I     VS2   62.4   58.0    334  4.20  4.23  2.63  4.0
   4   0.31     Good     J     SI2   63.3   58.0    335  4.34  4.35  2.75  5.0