how to number rows based on column values

[#1]

Hi All,

I have a table with SN and timestamp for each. I need to number the lines per each SN based on timestamp.

the table is sorted by time and I wanted to use ROW() with grouping by SN, but i don't know how to do it.

appreciate your help,

Thanks

[#2]

Here is the formula that I normally use

Col Cumulative Sum( 1, :SN );

[#3]

@jthi  did something similar with ColSum(); here's an explanation of how it works:

https://community.jmp.com/t5/Discussions/Countif-equivalent/m-p/664313/highlight/true#M85267

[#4]

If you cannot guarantee that the entries are sorted, use

Col Rank(:START_TIME_UTC,:SN)