diffs <- do.call(expand.grid, dt)
diffs$delta <- rowSums(expand.grid(dt$a, -dt$b))
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Arun Kumar Saha a ?crit :> Dear R Users,
>
> Suppose I have a dataset like this:
>
> a b
>
> 39700 485.00
> 39300 485.00
> 39100 480.00
> 38800 487.00
> 38800 492.00
> 39300 507.00
> 39500 493.00
> 39400 494.00
> 39500 494.00
> 39100 494.00
> 39200 490.00
>
> Now I want get a-b for all possible combinations of a and b. Using two
'for'
> loop it is easy to calculate. But problem arises when row length of the
data
> set is large eg. 1000 or more. Then R takes lot of time to do that. Can
> anyone please tell me whether there is any R-function to do such kind of
job
> quickly?
>
> Thanks and regards,
>
> [[alternative HTML version deleted]]
>
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