On 09/04/2009 8:07 AM, Richard Morey wrote:
Hi everyone,
I saw this problem dealt with here:
http://markmail.org/search/list:r-project?q=integrate#query:list%3Ar-project%20integrate+page:1+mid:qczmyzr676pgmaaw+state:results
but no one answered that request that I can tell. I'm having the same
problem. I'm having problems passing arguments to functions that I'd
like to integrate. I could swear this worked in the past, but I can't
get it to work now. I'm running R on Windows.
Here's my toy code to reproduce the problem:
R.Version()$version.string
# [1] "R version 2.8.1 (2008-12-22)"
f=function(x,const)
2^x+const
f2=Vectorize(f,c("x"))
testval=2
f2(1:5,testval)
# [1] 4 6 10 18 34
# The vectorized function seems to work right.
integrate(f2,.5,1,c=2)
# Works. Returns
# 1.845111 with absolute error < 2.0e-14
integrate(f=f2,.5,1,const=testval)
# Doesn't work. Returns
# Error in eval(expr, envir, enclos) :
# ..1 used in an incorrect context, no ... to look in
I understand that I don't have to Vectorize this function for it to
work, but the more complicated functions I'm using require Vectorization.
Why can't I pass the argument "const" as a variable, instead of a value?
I don't understand this error.
I'm not sure what's happening exactly; both Vectorize and integrate do
tricky things with evaluation frames, and it looks as though they are
not interacting well.
As a workaround, I'd suggest using a single argument function f instead:
> makef <- function(const) {
+ return(function(x) 2^x + const)
+ }
makef(testval) will capture the value of testval, so we don't need to
pass it, and then things work:
> f <- makef(testval)
> f2 <- Vectorize(f)
> integrate(f=f2, 0.5, 1)
1.845111 with absolute error < 2.0e-14
Duncan Murdoch
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