Eli -
I think you're looking for missing():
tst = function(a,b=1)
+ if(missing(a))print("You must provide a") else print(a)
tst()
[1] "You must provide a"
tst(7)
[1] 7
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
[email protected]
On Thu, 7 Oct 2010, Eli Holmes wrote:
I'm trying to test for the existence of an object within a function,
but despite searching the help files and R-list, I can't figure out
how to do it.
Here is some test code:
#-------------------------
a=1 #now I have a in the global environment
tst <- function(a,b=1) {
# but a is not in the local function environment
print(exists("a", inherits=FALSE)) #This is how I think I should be
able to test if it is in the local function environment
print(a)
}
tst()
#----------------------
#Here's the output
[1] TRUE
Error in print(a) : argument "a" is missing, with no default
It says TRUE, even though I specified inherits=FALSE and "a" is not in
the function environment. I've tried to pass in where and envir
arguments to exists() but I haven't been able to solve the problem.
Thanks in advance.
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
