Re: Suggestion: add the possibility to apply multiple operations to a single column (or multiple columns)

[Tomas Peitl]

Hi Tim,

Thanks for the reply.

> The main thing to be careful of with a "mean,max,count"-style 
> operation is how it would interact with groupby or crosstab. Eg I 
> wonder if "datamash groupby 1 mean,max,count 2" makes sense in any way.
>
> Ranges like 1-2,4 could be less straightforward, especially when 
> combined with the former idea of providing multiple operations 
> simultaneously. When preparing a test for "mean,max,count 1-2,4", 
> should the test output columns like "mean_1, max_1, count_1, mean_2, 
> max_2, count_2, mean_4, max_4, count_4", or "mean_1, max_1, count_1, 
> mean_2, max_2, count_2, mean_4, max_4, count_4", or something else?

Good points, I didn't even realize you would have to make a decision 
here. Perhaps it's more natural to think of 'mean,max' as a single 
combined operation, i.e. the ordering mean 1 max 1 mean 2 max 2, but I 
also originally had the other ordering in mind. But in any case, if this 
is what you need and you type it out verbosely, you still have to make 
that same decision, only here we would have to make a default decision 
for every case. There could even be a command-line switch to toggle the 
ordering.

> Is there any chance you could provide a preliminary patch and tests 
> which would get the ball rolling? You could break it up into two 
> patches, one for adding column ranges, and one for "lambda-ing" 
> multiple operations over a column.

Perhaps, but can't make any promises either.

Cheers,
Tomas