Expand columns of matrix in R

Question

I have a matrix "a" like the following:

a<-rbind(c("a1","ost1;ost2;ost3","utr;body;pro"), c("a2","idh1;idh2","pro;body"), c("a3","dnm1","body")) >a [,1] [,2] [,3] [1,] "a1" "ost1;ost2;ost3" "utr;body;pro" [2,] "a2" "idh1;idh2" "pro;body" [3,] "a3" "dnm1" "body"

I want to get a matrix "b" like this

 [,1] [,2] [,3] [1,] "a1" "ost1" "utr" [2,] "a1" "ost2" "body" [3,] "a1" "ost3" "pro" [4,] "a2" "idh1" "pro" [5,] "a2" "idh2" "body" [6,] "a3" "dnm1" "body"

OK, get it:

b<-do.call(rbind, (apply(a, 1, function(x) {do.call(cbind, strsplit(x,";"))})))

Feel free to post your solution as an answer and accept it.

Julius Vainora
– Julius Vainora

2013-06-17 14:16:46 +00:00
Commented Jun 17, 2013 at 14:16 — Julius Vainora
– Julius Vainora, Commented Jun 17, 2013 at 14:16
do.call is almost like magic :-) . Nice work.

Carl Witthoft
– Carl Witthoft

2013-06-17 14:56:46 +00:00
Commented Jun 17, 2013 at 14:56 — Carl Witthoft
– Carl Witthoft, Commented Jun 17, 2013 at 14:56

flodel · Accepted Answer · 2013-06-17 23:23:55Z

Your solution, without the unnecessary parentheses:

do.call(rbind, apply(a, 1, function(x) do.call(cbind, strsplit(x, ";"))))

This also works:

do.call(rbind, lapply(apply(a, 1, strsplit, ';'), do.call, what = cbind))

Not that there is anything wrong with using anonymous functions (function(x){...}), but some people find it more "elegant" without any.

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