[R] Conditional expand.grid()

[jim holtman]

?combn

> combn(10,2)
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[,13] [,14] [,15] [,16] [,17]
[1,]    1    1    1    1    1    1    1    1    1     2     2     2
 2     2     2     2     2
[2,]    2    3    4    5    6    7    8    9   10     3     4     5
 6     7     8     9    10
     [,18] [,19] [,20] [,21] [,22] [,23] [,24] [,25] [,26] [,27] [,28]
[,29] [,30] [,31] [,32] [,33]
[1,]     3     3     3     3     3     3     3     4     4     4     4
    4     4     5     5     5
[2,]     4     5     6     7     8     9    10     5     6     7     8
    9    10     6     7     8
     [,34] [,35] [,36] [,37] [,38] [,39] [,40] [,41] [,42] [,43] [,44] [,45]
[1,]     5     5     6     6     6     6     7     7     7     8     8     9
[2,]     9    10     7     8     9    10     8     9    10     9    10    10


On Sat, Jul 11, 2009 at 9:23 AM, Hesen Peng<hesen.peng at emory.edu> wrote:
> Hello my R buddies,
>
> I'm trying to generate a bivariate data.frame with the elements of
> first row greater than the second row. The more complicated method
> that I can think of is:
>
>   n <- 10
>   temp <- expand.grid(1:n,1:n)
>   temp<-temp[temp[,1]>temp[,2],]
>
> However, I guess there must be some easier way of doing this. Besides,
> if inequality condition is applied at the very beginning, this will
> save me a lot of memory if n goes to a very large number. Is there any
> suggestions? Thanks a lot.
>
> Best wishes,
>
> --
> 彭河森 Hesen Peng
> http://hesen.peng.googlepages.com/
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?