mapply to lapply
On Mon, Apr 18, 2011 at 2:10 PM, Alaios <alaios at yahoo.com> wrote:
Dear Andreas, I would like to thank you for your reply. I have tried two alternatives but none of the two worked out: F2[i+1,j+1]<-sum(lapply(1:nrow(cells), function(rowInd) Fwithcellvalue(i=i,j=j,a=cells[rowInd,2],b=cells[rowInd,4],c=cells[rowInd,1],d=cells[rowInd,3],e=cells[rowInd,5]))) this one is executed : takes like 2 mins to return(which is normal) but returns the following ^@Error in sum(lapply(1:nrow(cells), function(rowInd) Fwithcellvalue(i = i, ?: ?invalid 'type' (list) of argument
The lapply part worked but for sum you need a vector rather than a list (which is the result of lapply). So e.g. sum(unlist(lapply(..... something .....))) should work. KK
afterwards I tried to change the function definition so to pass i,j inside:
This one does not execute at all
F2[i+1,j+1]<-sum(lapply(1:nrow(cells), function(rowInd,i,j) Fwithcellvalue(i=i,j=j,a=cells[rowInd,2],b=cells[rowInd,4],c=cells[rowInd,1],d=cells[rowInd,3],e=cells[rowInd,5])))
Error in paste("f", i, j, "(a,b,c,d)", sep = "") :
?argument "i" is missing, with no default
What do you think I should try out now?
Vielen Dank
Alex
--- On Mon, 4/18/11, Andreas Borg <andreas.borg at unimedizin-mainz.de> wrote:
From: Andreas Borg <andreas.borg at unimedizin-mainz.de> Subject: Re: [R] mapply to lapply To: "Alaios" <alaios at yahoo.com> Cc: R-help at r-project.org Date: Monday, April 18, 2011, 11:10 AM My solution would be to use an index variable that goes from 1 to the number of rows that are to be processed, along with a helper function which calls Fwithcellvalue with the suitable arguments: F2[i+1,j+1]<-sum(lapply(1:nrow(cells), function(rowInd) Fwithcellvalue(i=i,j=j,a=cells[rowInd,2],b=cells[rowInd,4],c=cells[rowInd,1],d=cells[rowInd,3],e=cells[rowInd,5])) Best regards, Andreas Alaios schrieb:
Dear all, I would like to ask your help concerning converting a
mapply function to lapply. The reason is that I would like to use mclapply which requires lapply syntax.
The command I would like to convert is:
F2[i+1,j+1]<-sum(mapply(Fwithcellvalue,i=i,j=j,a=cells[,2],b=cells[,4],c=cells[,1],d=cells[,3],e=cells[,5]))
Could you please help me understand how I should
change it?
Best Regards Alex
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______________________________________________ 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.