Question

I have a data set that looks something like this:

0 Var1 Var 2 Var3 Var4
1 2|1
2 1|2
3            1|2
4            2|1
5                  2|1
6                  2|1
7       1|2
8       1|2

I would like to collapse to the left so as to make it look something like this:

0 G.F  G.F.1
1 2|1  Var1
2 1|2  Var1
3 1|2  Var2
4 2|1  Var2
5 2|1  Var3
6 2|1  Var3
7 1|2  Var4
8 1|2  Var4

I have a general idea involving the reshape package, but as of yet have not found an elegant solution.

Answer 1

Try this:

library(reshape)
foo = data.frame(Var1=c("2|1","1|2","","",""),Var2=c("","","","","1|2"))
foo 
#   Var1 Var2
# 1  2|1     
# 2  1|2     
# 3          
# 4          
# 5       1|2

foo = cbind("Row"=seq(nrow(foo)),foo)
foo = melt(foo, "Row")
setNames(foo[foo$value!="", c(3,2)], c("G.F","G.F.1"))
#    G.F G.F.1
# 1  2|1  Var1
# 2  1|2  Var1
# 10 1|2  Var2