Re: [R] loop and sapply problem, help need

From: Ram H. Sharma <sharma.ram.h_at_gmail.com>
Date: Sat, 09 Apr 2011 17:27:44 -0400

Hi Phil and R users

Let me clear my problem. The generating sample is not prime issue here. I am simulating a situation, for which I need to sample. But once I have sampling done, I need to do a conditional decoding. Let me clear it with more clear data example:

x <- read.table(textConnection("
mark lcd1 lcd2 lcd3 PR1 PR2 PR3 PR4
1 11 22 12 1 2 3 1
2 33 44 34 1 2 3 1
3 22 44 24 3 1 2 1
4 11 33 13 2 2 1 3
5 22 11 12 3 2 2 1 "), header = TRUE)

I want to do a conditional formatting of PR1:PR4 (in real sense I have
>20000 such variables) based on corrsponding value in variable column lcd1
or lcd2 or lcd3.

mark lcd1 lcd2 lcd3 PR1 PR2 PR3 PR4

1       11     22   12      1     2     3      1
2       33      44  34      1     2     3      1
3       22      44  24      3    1      2      1
4      11       33  13      2    2      1      3
5       22      11  12      3    2      2      1

If PR1 =1, then PR1= lcd1

   PR1=2, then PR1 = lcd2
   PR1=3, then PR1 = lcd3

     similarly for PR2...................to end of files PR4

#Expected Output
mark lcd1 lcd2 lcd3 PR1 PR2 PR3 PR4
1 11 22 12 11 22 12 11
2 33 44 34 33 44 34 33
3 22 44 24 24 22 44 22
4 11 33 13 33 33 11 13
5 22 11 12 12 11 11 22

Thank you;

Ram H

On Sat, Apr 9, 2011 at 4:13 PM, Phil Spector <spector_at_stat.berkeley.edu>wrote:

> 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]]
>>
>> ______________________________________________
>> R-help_at_r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>

-- 

Ram H

	[[alternative HTML version deleted]]

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Received on Sat 09 Apr 2011 - 21:33:55 GMT

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