Dear R Helpers, I want to test if a procedure within a loop has produced an error or not. If the procedure has produced an error, then I want to ignore its result. If it has not produced an error, then I want to use the result. The problem In order to run the loop without crashing if the procedure produces an error, I place the routine inside a try() statement.
So, suppose I am trying to find the predicted values for a regression in a loop If the procedure now produces an error, I can detect it with:- if grep('Error', result)<1 #and so choose not use the result but if the procedure does not produce an error, then "if grep('Error', result)<1" now produces the result logical(0) and the loop then fails with the message set.seed(1) cumulator=rep(0,100) for (i in 1:100){ y1=rnorm(100) x0=rbinom(100,1,0.02) x1=rbinom(100,1,0.5) x2=rbinom(100,1,0.5) x1[x0]=NA dat=data.frame(y1,x1) result=try(lm(y1~x1, na.action=na.fail, data=dat),T); print(result) x1=x2; dat2=data.frame(x1) if (grep('Error',result)<1) cumulator=cumulator+predict(result,x2) } The above runs and rejects the 'result' until i=6, when lm runs and grep('Error', result) gives:- Error in if (grep("Error", pred1) < 1) for (i in labels(pred1)) votes[rownames(votes) == : argument is of length zero but, predict(result,dat2) runs fine. So, how do I trap or use the 'logical(0)' state of grep('Error', result) to obtain and accumulate my result? Thanks in advance for your help Jonathan Williams ______________________________________________ R-help@stat.math.ethz.ch 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.