Hi
Well, no data so a wild guess. You want select values from matrix sr based
on values in borders[,1] and borders[,2].
If it is the case plain selection could be far better
> mat<-matrix(1:12, 4,4)
> mat
[,1] [,2] [,3] [,4]
[1,] 1 5 9 1
[2,] 2 6 10 2
[3,] 3 7 11 3
[4,] 4 8 12 4
> b1<-sample(1:4, 3)
> b2<-sample(1:4, 3)
> cbind(b1,b2)
b1 b2
[1,] 3 2
[2,] 4 1
[3,] 2 3
> mat[cbind(b1,b2)]
[1] 7 4 10
>
If you want something else please provide some sample code and data which
can be used for reproduction of your problem.
>From the error it seems that your function is somehow incompatible with
mapply expectation.
Regards
Petr
r-help-boun...@r-project.org napsal dne 03.02.2011 10:59:34:
> Goodmorning List Member,
> I would like to ask your help using mapply or Vectorize to make a loop
more efficient.
> I have a m*4 matrix called borders and I would like to add a 5th column.
Thus first
> A. I add the new 5th column
> borders<-cbind(borders,matrix(data=NA,nrow=nrow(borders)))
> B. For every cell in this new column I call a function and I put the
results in
> for (i in c(1:nrow(borders))) # How can I can improve that with mapply?
> borders[i,5]<-findCell(c(borders[i,1],borders[i,2]),sr)
>
> As you can see from B I call a function called findCell that takes as
input
> two arguments
> -x: a vector with two cells thus the c(borders[i,1],borders[i,2])
> -sr: a matrix that is always the same (this input is always constant)
>
> Then I tried to change the loop in B and use mapply.
> mapply(findCell,x=cbind(test[,1],test[,2]),sr=sr)
> > Error in if (!is.finite(length.out) || length.out < 0L)
> > stop("length must be non-negative number") else if
> > (length.out == :
> > missing value where TRUE/FALSE needed
> > Calls: mapply -> .Call -> <Anonymous> -> seq
> > -> seq.default
>
> I would be grateful if you can help me understand me what this error
message is about.
>
> Best Regards
> Alex
>
>
>
>
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