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Feature Request: "matrix[1:10,1:10, block=F] <- 1:10"

3 messages · Warnes, Gregory R, David Meyer, David Brahm

Warnes, Gregory R
# 
Hi Guys,

I've again been surprised when something like
gives block-wise application of the assignment:

     [,1] [,2] [,3]
[1,] "b"  "b"  "b" 
[2,] "a"  "a"  "a" 
[3,] "c"  "c"  "c" 

when what I wanted was by-element assignment:

     [,1] [,2] [,3]
[1,]   ""   ""  "b"
[2,]  "a"   ""   ""
[3,]   ""  "c"   ""


I always end up writing the code:
to do what I want.

So, I'm thinking about creating a patch to the R source to add an optional
parameter, say "block",  to the "[<-" call for matrixes and data frames.  

When "block=T" (the default) the old behaviour is preserved.  When "block=F"
the behavior I want occures so that
would do what I want.


Comments?  Cheers?  Jeers?  Silence?


-Greg

 



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David Meyer
#
"Warnes, Gregory R" wrote:
Yes, you need to provide the indices as matrix, like:

m[cbind(index_i,index_j)]

(BTW: Hou do you manage to get index_i <- c(...) properly working? My R
version still treats _ as a replacement for <-)

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      David Brahm
    

    

      
      #
    

  


  

      
Gregory R Warnes <gregory_r_warnes@groton.pfizer.com> wrote:

        
R> m <- matrix("", nrow=3,ncol=3)
 R> index_i <- c(2,1,3)
 R> index_j <- c(1,3,2)
 R> vals    <- c("a","b","c")
 R> m[ index_i, index_j ] <- vals

but what he wants to get is:
 >      [,1] [,2] [,3]
 > [1,]   ""   ""  "b"
 > [2,]  "a"   ""   ""
 > [3,]   ""  "c"   ""

Just do this instead:
 R> m[ cbind(index_i, index_j) ] <- vals