New to koalas and trying to do something really basic. I am simply trying to count the unique values in a column in an aggregation. In pandas I would do:
df.groupby('columnname').agg({'column_i_want_count_of_unique_values' : pd.Series.nunique})
But for example ks.Series.nunique doesn't work and 'count' also does not seem to give the right answer.
Pretty frustrating for something so simple and common, and annoying that I can't seem to find it in the documentation for something that bills itself as porting pandas to spark.