[R] Why doesn't this nested loop work?

[Peter Dalgaard]

"Teresa Nelson" <jtanelson at centurytel.net> writes:

> Hi there,
> 
>  
> 
> I can get the for-loop to work, I can get the while loop to work.  But I
> can't get a for loop to work nested within the while loop - why?  
> 

What do you mean it doesn't work??

I get:

>
> results
       [,1] [,2]
  [1,]    1   25
  [2,]    2   50
  [3,]    3   75
  [4,]    4  100
  [5,]    5  125
  [6,]    6  150
  [7,]    7  175
  [8,]    8  200
  [9,]    9  225
 [10,]   10  250
 [11,]   11  275
 [12,]   12  300
 [13,]    0    0
...
[107,]    0    0
[108,]  108  300
[109,]    0    0
[110,]  110  275
[111,]    0    0
[112,]    0    0
[113,]    0    0
[114,]    0    0
[115,]    0    0
[116,]    0    0
[117,]    0    0
[118,]    0    0
[119,]    0    0
[120,]  120  300

If that's not what you expected, then you need to adjust your
expectations. Notice that your k's are effectively

> outer(1:12,1:10)
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    1    2    3    4    5    6    7    8    9    10
 [2,]    2    4    6    8   10   12   14   16   18    20
 [3,]    3    6    9   12   15   18   21   24   27    30
 [4,]    4    8   12   16   20   24   28   32   36    40
 [5,]    5   10   15   20   25   30   35   40   45    50
 [6,]    6   12   18   24   30   36   42   48   54    60
 [7,]    7   14   21   28   35   42   49   56   63    70
 [8,]    8   16   24   32   40   48   56   64   72    80
 [9,]    9   18   27   36   45   54   63   72   81    90
[10,]   10   20   30   40   50   60   70   80   90   100
[11,]   11   22   33   44   55   66   77   88   99   110
[12,]   12   24   36   48   60   72   84   96  108   120

and that in that table some numbers occur up to five times and others
not at all.

  
> 
> Please help,
> 
> Teresa
> 
> 
> #  Why doesn't this nested loop work?
> 
> n.max <- 300
> NUM <- 25
> 
> n.sim <- 10 
> j <- (n.max/NUM)*n.sim
> 
> results <- matrix(0, nrow=j, ncol=2)
> 
> while(NUM <= n.max){
> 
> for(i in 1:n.sim){
> 
> k <- (NUM/25)*i
> 
> results[k,1] <- k
> results[k,2] <- NUM
> 
> } 
> 
> NUM <- NUM + 25
> 
> }
> 
> results
> 
> #### TRY WHILE LOOP ONLY
> 
> results <- matrix(0, nrow=12, ncol=2)
> 
> n.max <- 300 
> NUM <- 25
> 
> while(NUM <= n.max){ 
> 
> k <- NUM/25
> 
> results[k,1] <- k 
> results[k,2] <- NUM 
> 
> NUM <- NUM + 25
> 
> }
> 
> results
> 
> # It works, here are the results
> 
> #      [,1] [,2]
> # [1,]    1   25
> # [2,]    2   50
> # [3,]    3   75
> # [4,]    4  100
> # [5,]    5  125
> # [6,]    6  150
> # [7,]    7  175
> # [8,]    8  200
> # [9,]    9  225
> #[10,]   10  250
> #[11,]   11  275
> #[12,]   12  300
> 
> 
> 
> ### Try For Loop Only 
> 
> n.sim <- 10
> NUM <- 25
> 
> results <- matrix(0, nrow=10, ncol=2)
> 
> for(i in 1:n.sim){
> 
> results[i,1] <- i
> results[i,2] <- NUM
> 
> } 
> 
> results
> 
> # it works, here are the results 
> #      [,1] [,2]
> # [1,]    1   25
> # [2,]    2   25
> # [3,]    3   25
> # [4,]    4   25
> # [5,]    5   25
> # [6,]    6   25
> # [7,]    7   25
> # [8,]    8   25
> # [9,]    9   25
> #[10,]   10   25
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-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907