Return value from function when iterating in a loop R
25,723
The problem is that you do not get the result of your function:
inPvec<-c() #predefine vector to concatenate results into
for (x in tabs){ #tabs holds multiple tables as a list
inPvec<-c(inPvec,myFunction(x)) #concatenate results from each iteration
}
and you should correct your function too:
myFunction<-function(tab){ #takes tabular input
inP <- c()
for (x in 1:dim(tab)[1]){ #iterate over rows
rname<-rownames(tab)[x] #rownames as output
if(rname=="something") inP<-c(inP,rname) #trivial work
}
return(inP) #return the vector made above
}
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Comments
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bruce01 over 3 years
I have stayed away from functions in R but decided it is better practice. Now I have this issue. I write my function:
myFunction<-function(tab){ #takes tabular input inP<-c() for (x in 1:dim(tab)[1]){ #iterate over rows rname<-rownames(tab)[x] #rownames as output if(rname<5) inP<-c(inP,rname) #trivial work } return(inP) #return the vector made above } tablist<-as.list(paste("tab",1:4,sep="")) for (x in 1:length(tablist)){ tablist[[x]]<-table(c(1:10),c(1:10)) } inPvec<-c() #predefine vector to concatenate results into for (x in 1:length(tablist)){ #tabs holds multiple tables as a list myFunction(tablist[[x]]) #run myFunction for each table held in tabs inPvec<-c(inPvec,inP) #concatenate results from each iteration } inP #NULL myFunction(tablist[[1]]) #[1] "1" "2" "3" "4" "10"
Edited as workable example: apologies for laziness.
If you run for the loop in the example, inP returns NULL, as does inPvec. Bu running single tables in the function return the correct value. However, inP is NULL on calling it, so I guess this is where my issue is.
I want everything from the loop iterating over the function to be returned to a single vector eg:
inPVec #[1] "1" "2" "3" "4" "10" "1" "2" "3" "4" "10" "1" "2" "3" "4" "10" etc
Any help much appreciated.
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Paul Hiemstra over 10 yearsPlease help us help you by providing us with a reproducible example (i.e. code and example data), see stackoverflow.com/questions/5963269/… for details.
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bruce01 over 10 yearsSorry, edited now to run as standalone example.
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bruce01 over 10 yearsYes, sorry again, inP was meant to be defined inside the function.
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bruce01 over 10 yearsGreat, thanks Karl, I understand: the return value is myFunction(x), as opposed to the value defined and returned in myFunction (eg inP).
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WestCoastProjects almost 6 yearswhat an "interesting" / different syntax
R
uses for concatenation. Glad to have stumbled onto this answer.