[R] (no subject)

[David Winsemius]

On Aug 19, 2012, at 5:14 PM, Dikán Szabolcs András wrote:

> Dear R Users! I'm new in R! I've got a data.frame. For  
> example:a<-data.frame(cbind(  0:1,   1:10))   X1 X2
> 1   0  1
> 2   1  2
> 3   0  3
> 4   1  4
> 5   0  5
> 6   1  6
> 7   0  7
> 8   1  8
> 9   0  9
> 10  1 10 Firstly i want to create combinations from  X2, for  
> example:combn(a$X2,2) It's ok,
> but secondly



> I would like to get combinations from those X2 numbers only , where  
> X1= 0. Could you help me? Thanks!

 > combn( a[a$X1==0, "X2"] ,2)
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]    1    1    1    1    3    3    3    5    5     7
[2,]    3    5    7    9    5    7    9    7    9     9

>
> 	[[alternative HTML version deleted]]

Please learn to post with a meaningful subject line and in plain text.  
The most excellent Posting Guide is a font of wisdom in other areas as  
well. As is the "Introduction to R" which should be studied in its  
entirety but for this case the section: "2.7 Index vectors; selecting  
and modifying subsets of a data set".


Afore-mentioned posting guide: http://www.R-project.org/posting-guide.html

-- 

David Winsemius, MD
Alameda, CA, USA