[R] How to expand.grid with string elements (the half!)
William Dunlap
wdunlap at tibco.com
Mon Jun 10 18:55:55 CEST 2013
Perhaps the OP wants the unique combinations of V1 and V2, as in
R> d <- expand.grid(V1=c("x","y","z"),V2=c("x","y","z"))
R> d[ as.numeric(d$V1) <= as.numeric(d$V2), ]
V1 V2
1 x x
4 x y
5 y y
7 x z
8 y z
9 z z
or
R> V <- letters[24:26]
R> rbind(t(combn(V,m=2)), cbind(V,V))
V V
[1,] "x" "y"
[2,] "x" "z"
[3,] "y" "z"
[4,] "x" "x"
[5,] "y" "y"
[6,] "z" "z"
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Rolf Turner
> Sent: Monday, June 10, 2013 2:20 AM
> To: Gundala Viswanath
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] How to expand.grid with string elements (the half!)
>
>
> Your question makes no sense at all. The grid expansion
> has 9 rows. In case you hadn't noticed, 9 is an odd number
> (i.e. not divisible by 2). There are no "halves".
>
> Do not expect the list to read your mind. Instead, ask a
> meaningful question.
>
> cheers,
>
> Rolf Turner
>
> On 10/06/13 17:25, Gundala Viswanath wrote:
> > I have the following result of expand grid:
> >
> >> d <- expand.grid(c("x","y","z"),c("x","y","z"))
> > What I want is to create a combination of strings
> > but only the half of the all combinations:
> >
> > Var1 Var2
> > 1 x x
> > 2 y x
> > 3 y y
> > 4 z y
> > 5 x z
> > 6 z z
> >
> >
> > What's the way to do it?
>
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