implement similar functions for polars

[samukweku]

in relation to #1343 - this is a list of functions missing in the polars library that could be implemented :

• [x] clean_names
• [x] pivot_longer
• [ ] pivot_wider
• [x] xlsx_tables
• [x] xlsx_cells
• [x] read_commandline
• [ ] conditional_join
• [x] complete
• [ ] ~expand_grid~ pl.join with how='cross' covers this
• [x] convert_excel_date
• [x] convert_matlab_date
• [ ] ~convert_unix_date~ pl.from_epoch covers this
• [ ] ~bin_numeric~ pl.Expr.cut covers this
• [ ] ~concatenate_columns~ can be replicated with pl.concat_str
• [ ] ~deconcatenate_columns~ pl.Expr.str.split covers this
• [ ] ~factorize_columns~ pl.rank(dense) or pl.Expr.to_physical covers this
• [ ] ~get_dupes~ Expr.is_duplicated() covers this
• [ ] jitter
• [ ] limit_column_characters
• [ ] min_max_scale
• [ ] ~move~ can be replicated with polars' selectors
• [x] row_to_names
• [ ] ~shuffle~ pl.Expr.shuffle covers this
• [ ] sort_naturally
• [ ] ~take_first~ group_by.first() covers this
• [ ] also

Care should be taken to not create the function, if an existing solution already exists for any of these functions (probably named differently, or a combination of existing polars functions that covers all use cases of any of the listed functions above)

[samukweku]

the current pivot_longer implementation is not good enough. I'll submit a PR with improvements

[samukweku]

I assumed (wrongly) that polars' join maintains order (it only does so for left join). need to rethink the computation logic for complete. I'll submit a PR with improvements

[3SMMZRjWgS]

eagerly awaits for 0.28.0 release!