pub fn concat_dataframes(frames: &[&DataFrame]) -> Result<DataFrame, FrameError>Expand description
Concatenate DataFrames along axis 0 (row-wise).
Matches pd.concat([df1, df2, ...], axis=0) semantics:
- Output columns are the union of input columns (
join='outer'). - Index labels are concatenated in order (duplicates preserved).
- Missing cells materialize as
Scalar::Null. - Empty input returns an empty DataFrame.