Index by group with collapse...

How to translate data.table code to collapse...

summarise/collapse dataframe by row above or below based on conditions...

collapse package: sum over two vectors but keep empty intersections...

Grouped means in collapse package...

Collapsing rows into lists for multiple columns based on identified duplicates in a group of other c...

R combine rows in data frame based on grouping variable when there are both numeric and character co...

Error: 'across' is not an exported object from 'namespace:collapse'...