 Dear R Users! I&#39;m new in R! I&#39;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&#39;s ok, butsecondly I would like to get combinations from those X2 numbers only , where X1= 0. Could you help me? Thanks!          
	[[alternative HTML version deleted]]


