# [R] loop and sapply problem, help need

Phil Spector spector at stat.berkeley.edu
Sat Apr 9 22:13:03 CEST 2011

```Ram -
I think you'll have to explain what you're trying to do.
First, you're creating a 10x10 matrix newd, which could
be done a bit more efficiently by using

newd = matrix(sample(c(1,2,3,3,),10*length(pvec),replace=TRUE),ncol=10)

Notice that calling sapply on a matrix applies the function to each
element of the matrix.

But your fun3 function really doesn't make sense, since you are
testing each scalar element for equality to a scalar, and then setting
it equal to a vector.  It seems to me that what you're trying to do is

smpool = c(1,2,3,3)
allvals = rbind(lcd1,lcd2,lcd3)
pn = replicate(10,allvals[sample(smpool,1),])

but I can't be sure.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spector at stat.berkeley.edu

On Sat, 9 Apr 2011, Ram H. Sharma wrote:

> Dear R experts
>
> Sorry for this question
>
> M1 <- 1:10
> lcd1 <- c(11, 22, 33, 44, 11, 22, 33, 33, 22, 11)
> lcd2 <- c(22, 11, 44, 11, 33, 11, 22, 22, 11, 22)
> lcd3 <- c(12, 12, 34, 14, 13, 12, 23, 23, 12, 12)
>
> #generating variables through sampling
> pvec <- c("PR1", "PR2", "PR3", "PR4", "PR5", "PR6", "PR7", "PR8", "PR9",
> "PR10")
> fun11 <- function(x){
>   smpool <- c(1,2,3,3)
>  x <-  sample(smpool, 10, replace= TRUE)
>  }
> newd <- sapply (pvec, fun11)
>
>
> # function to recode this new generated data
> fun3 <- function(x) {
>       (if ( x ==1){
>      x = lcd1
>    }else  if (x ==2){
>        x = lcd2
>    }  else if ( x ==3 ){
>         x = lcd3
>        } else x = NA )
>                return(x)
>              }
> Applying the function:
> pn <- sapply (newd, fun3)
>
> I am getting 10 x 100 matrix, in contrast to 10 x 10 what I am expecting !
>
> My objective here is to replace data points in all variables in newd
> with corresponding value with values vector lcd1 or lcd2 or lcd3 depending
> upon whether they are 1 or 2 or 3.
> For example;
>
> lcd1 <-   c(11, 22, 33, 44, 11, 22, 33, 33, 22, 11)
> lcd2 <-   c(22, 11, 44, 11, 33, 11, 22, 22, 11, 22)
> lcd3 <-   c(12, 12, 34, 14, 13, 12, 23, 23, 12, 12)
>
> PR1 <-    c(1,   2,   3,    2,   1,  1,   1,   2, 3,   1)
>
> with the new
> PR1n <- c(11,  11,   34,  11,  11, 22, 33, 22, 12, 11)
> # as the first element of this vector is determined by PR1[1] indicator
> determines whether to pick lcd1[1] or lcd2[1] or lcd3[1] element
> similarly for PR1[2] indicator whether to pick lcd1[2] or lcd2[2] or lcd3[2]
> element
>
> The same process need to be continued other PR2 to PR10 variables. That's
> why I attempted to use sapply.
>
> Thank you for your help
>
>
> --
>
> Ram H
>
> 	[[alternative HTML version deleted]]
>
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