[R] foreach returns null first object in the list

[Simon Zehnder]

Use an extra call to return:

post.ls <- foreach(i =1:2, .verbose = TRUE) %dopar% {

            fun <- func.list[[i]]
        	 if (i == 1) return(fun(Xa, Sa))
	 if (i == 2) return(fun(Ta, Sa))
            }

Best

Simon

On Sep 17, 2013, at 11:55 AM, pakoun <pkount at bgc-jena.mpg.de> wrote:

> Dear all,
> 
> I am sending you a copy of a demo that i am trying to make that work and
> embedded in a more complicated structure. The problem is that i want to get
> a list of 2 objects (matrices in specific, and thats why i am not specifing
> a .combine argument if i am not wrong..), but the first element of the list
> is just null. the second one is perfectly fine. Any idea?
> Thank you in advance
> 
> library(doMC)
> registerDoMC(2)
> 
> Xa<-matrix(1:100,ncol=10)
> Sa<-matrix(101:200,ncol=10)
> Ta<-matrix(1:100,ncol=10)
>   get.Xp <- function(Xa,Sa){
>             result <- Xa%*%Sa
>             return(result)
>   }
>   get.Sa.post <- function(Xa,Ta){
> 
>             result <- Ta%*%Sa
>             return(result)
>   }
> 
>  func.list <- list(get.Xp,get.Sa.post)   
> 
>  post.ls <- foreach(i =1:2) %dopar% {
> 
>             fun <- func.list[[i]]
>             if(i==1){fun(Xa,Sa)}
>             if(i==2){fun(Ta,Sa)}
> 
>             }
> 
> post.ls
> [[1]]
> NULL
> 
> [[2]]
>        [,1]   [,2]   [,3]   [,4]   [,5]   [,6]   [,7]   [,8]   [,9]  [,10]
> [1,] 154855 169455 184055 198655 213255 227855 242455 257055 271655 286255
> [2,] 155910 170610 185310 200010 214710 229410 244110 258810 273510 288210
> [3,] 156965 171765 186565 201365 216165 230965 245765 260565 275365 290165
> [4,] 158020 172920 187820 202720 217620 232520 247420 262320 277220 292120
> [5,] 159075 174075 189075 204075 219075 234075 249075 264075 279075 294075
> [6,] 160130 175230 190330 205430 220530 235630 250730 265830 280930 296030
> [7,] 161185 176385 191585 206785 221985 237185 252385 267585 282785 297985
> [8,] 162240 177540 192840 208140 223440 238740 254040 269340 284640 299940
> [9,] 163295 178695 194095 209495 224895 240295 255695 271095 286495 301895
> [10,] 164350 179850 195350 210850 226350 241850 257350 272850 288350 303850
> 
> 
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/foreach-returns-null-first-object-in-the-list-tp4676303.html
> Sent from the R help mailing list archive at Nabble.com.
> 
> ______________________________________________
> 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.