Koalas

Other new features and improvements

We added the following new features:

koalas:

- `to_numeric` (1060)

koalas.DataFrame:

- `idxmax` (1054)
- `idxmin` (1054)
- `pct_change` (1051)
- `info` (1124)

koalas.Index

- `fillna` (1102)
- `min` (1114)
- `max` (1114)
- `drop_duplicates` (1121)
- `nunique` (1132)
- `sort_values` (1120)

koalas.MultiIndex:

- `levshape` (1086)
- `min` (1114)
- `max` (1114)
- `sort_values` (1120)

koalas.SeriesGroupBy

- `head` (1050)

koalas.DataFrameGroupBy

- `head` (1050)


Other improvements

- Setting index name / names for Series (1079)
- disable 'str' for 'SeriesGroupBy', disable 'DataFrame' for 'GroupBy' (1097)
- Support 'compute.ops_on_diff_frames' for NumPy ufunc compay in Series (1128)
- Support arithmetic and comparison APIs on same DataFrames (1129)
- Fix rename() for Index to support MultiIndex also (1125)
- Set the upper-bound for pandas. (1137)
- Fix _cum() for Series to work properly (1113)
- Fix value_counts() to work properly when dropna is True (1116, 1142)

Other new features, improvements and bug fixes

We added the following new features:

Series:

- `factorize` (1972)
- `sem` (1993)

DataFrame

- `insert` (1983)
- `sem` (1993)

In addition, we also implement new parameters:

- Add min_count parameter for Frame.sum. (1978)
- Added ddof parameter for GroupBy.std() and GroupBy.var() (1994)
- Support ddof parameter for std and var. (1986)

Along with the following fixes:

- Fix stat functions with no numeric columns. (1967)
- Fix DataFrame.replace with NaN/None values (1962)
- Fix cumsum and cumprod. (1982)
- Use Python type name instead of Spark's in error messages. (1985)
- Use object.\_\_setattr\_\_ in Series. (1991)
- Adjust Series.mode to match pandas Series.mode (1995)
- Adjust data when all the values in a column are nulls. (2004)
- Fix as_spark_type to not support "bigint". (2011)