R help - Jul 2006 - Problem with allp ossible combination.

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]]

>Now I want get a-b for all possible combinations of a and b.
outer(a,b,"-")

hth
ido

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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