In R, I want to create a function that return Flag=0 if it encounters any error:
Error<-function(x){
tryCatch(x,
error=function(e{
Flag=0
}
)
}
When I enter: Error(5+b). It does not reflect Flag=0.
2 Answers
Flag <- 1
tryCatch(
5+b,
error=function(e) { Flag <<- 0}
)
Flag
[1] 0
In your code, the scope of Flag is local to the error handler. Using <<- makes the assignment in the global environment.
2 Comments
Ussu20
Instead if I use tryCatch(x,..) and outside the function, I define few expressions as: y<-20, a<-5 and x<- sqrt(y)+ a+"b". error(x) does not return Flag=0
Limey
@r2evan's comments above are worth noting. I accept my answer here is a simplistic approach that does not cater for every situation.
You can return a string ('error') here if error occurs and check it's value to return 1/0.
Error<-function(x){
y <- tryCatch(x,error=function(e) return('error'))
as.integer(y != 'error')
}
Error(sqrt('a'))
#[1] 0
Error(sqrt(64))
#[1] 1
1 Comment
Ussu20
I don't want tryCatch to evaluate and return output, I have a function that throws error. I just want it to assign a value of 0 if there is an error and a value of 1 if no error. can you please help with this?
list(Flag=0), or are you trying to assign the value0to an object namedFlagin the calling environment? Or do you just want it to return0?assign. The use of<<-(as in the answer) somewhat works, but does not allow you to control in which environment the variable is placed. For instance, if this is called from another function, then (1) if that function has aFlagobject in its environment, then that object is assigned0, otherwise (2)Flagis created/overridden in the global environment.