/pandas 0.23

pandas.Series.cummax

`Series.cummax(axis=None, skipna=True, *args, **kwargs)` [source]

Return cumulative maximum over a DataFrame or Series axis.

Returns a DataFrame or Series of the same size containing the cumulative maximum.

Parameters: axis : {0 or ‘index’, 1 or ‘columns’}, default 0 The index or the name of the axis. 0 is equivalent to None or ‘index’. skipna : boolean, default True Exclude NA/null values. If an entire row/column is NA, the result will be NA. *args, **kwargs : Additional keywords have no effect but might be accepted for compatibility with NumPy. `cummax : scalar or Series`

`pandas.core.window.Expanding.max`
Similar functionality but ignores `NaN` values.
`Series.max`
Return the maximum over Series axis.
`Series.cummax`
Return cumulative maximum over Series axis.
`Series.cummin`
Return cumulative minimum over Series axis.
`Series.cumsum`
Return cumulative sum over Series axis.
`Series.cumprod`
Return cumulative product over Series axis.

Examples

Series

```>>> s = pd.Series([2, np.nan, 5, -1, 0])
>>> s
0    2.0
1    NaN
2    5.0
3   -1.0
4    0.0
dtype: float64
```

By default, NA values are ignored.

```>>> s.cummax()
0    2.0
1    NaN
2    5.0
3    5.0
4    5.0
dtype: float64
```

To include NA values in the operation, use `skipna=False`

```>>> s.cummax(skipna=False)
0    2.0
1    NaN
2    NaN
3    NaN
4    NaN
dtype: float64
```

DataFrame

```>>> df = pd.DataFrame([[2.0, 1.0],
...                    [3.0, np.nan],
...                    [1.0, 0.0]],
...                    columns=list('AB'))
>>> df
A    B
0  2.0  1.0
1  3.0  NaN
2  1.0  0.0
```

By default, iterates over rows and finds the maximum in each column. This is equivalent to `axis=None` or `axis='index'`.

```>>> df.cummax()
A    B
0  2.0  1.0
1  3.0  NaN
2  3.0  1.0
```

To iterate over columns and find the maximum in each row, use `axis=1`

```>>> df.cummax(axis=1)
A    B
0  2.0  2.0
1  3.0  NaN
2  1.0  1.0
```

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