loop within a loop in R -

i'm trying write loop within loop in r, seems inner loop working:

test <- rbind(c(1:30), c(31:60), c(61:90), c(91:120)) 

here's i've been written:

b<- data.frame() n<-1 i<-1 c<- data.frame()  while(i<=4){     while(n<=10) {         a<-cbind(test[i, 3*n-2], test[i, 3*n-1], test[i,3*n])         b<-rbind(b,a); n<-n+1     } ; i<-i+1; c<-cbind(c,b) } 

basically i'm trying group each line 3 columns , transform multiple lines, , every line , bind these columns.

my desired output like:

   1  2  3  31  32  33  61  62  63  81  82  83    4  5  6  34  35  36  64  65  66  84  85  86    7  8  9  37  38  39  67  68  69  ......   10 11 12  40  41  42  ......   13 14 15  43  45  46   16 17 18 ......   19 20 21   22 23 24   25 26 27   28 29 30  58  59  60  78  79  80  118 119 120 

however have written work first line, apparently outer loop doesn't work. what's wrong please?

edit: here's further tried in response loop:

b<- data.frame() c<- data.frame() for(i in seq(from = 1, = 4, =1)){     for( n in seq(from=1, to=10, by=1)) {         <- cbind(test[i, 3*n-2], test[i, 3*n-1], test[i,3*n])         b <- rbind(b,a)     }         c <- cbind(c,b) } 

but still not make work. what's wrong it?

this might make life bit easier...

out <- lapply( data.frame( t(test) ) , matrix , ncol = 3 , byrow = true ) res <- do.call( cbind , out )     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]  [1,]    1    2    3   31   32   33   61   62   63    91    92    93  [2,]    4    5    6   34   35   36   64   65   66    94    95    96  [3,]    7    8    9   37   38   39   67   68   69    97    98    99  [4,]   10   11   12   40   41   42   70   71   72   100   101   102  [5,]   13   14   15   43   44   45   73   74   75   103   104   105  [6,]   16   17   18   46   47   48   76   77   78   106   107   108  [7,]   19   20   21   49   50   51   79   80   81   109   110   111  [8,]   22   23   24   52   53   54   82   83   84   112   113   114  [9,]   25   26   27   55   56   57   85   86   87   115   116   117 [10,]   28   29   30   58   59   60   88   89   90   118   119   120 

possibly easier do...

do.call( cbind , lapply( 1:4 , function(x) matrix( test[x,] , ncol = 3 , byrow = f ) ) ) 

if insist on using for loop easiest way...

out <- numeric() for( in 1:4 ){   tmp <- matrix( test[ , ] , ncol = 3 , byrow = true )   out <- cbind( out , tmp )   } 

the problem stemmed use of out <- data.frame initialise result data structure. meant trying cbind data.frame no rows 1 10 rows. not possible (although intuitively being able cbind empty vector 10 row matrix should fail doesnt!).