dfr max for expression> dfr max {flags} 
| input | output | 
|---|---|
| any | any | 
Max value from columns in a dataframe
> [[ab]; [62] [14] [41]] |dfr into-df|dfr max
╭───┬───┬───╮
│# │ a │ b │
├───┼───┼───┤
│0│6│4│
╰───┴───┴───╯
Max aggregation for a group-by
> [[ab]; [one2] [one4] [two1]]
|dfr into-df
|dfr group-bya
|dfr agg (dfr colb|dfr max)
╭───┬─────┬───╮
│# │  a  │ b │
├───┼─────┼───┤
│0│one│4│
│1│two│1│
╰───┴─────┴───╯
Tips: Dataframe commands were not shipped in the official binaries by default, you have to build it with --features=dataframe flag
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    https://www.nushell.sh/commands/docs/dfr_max.html