On Feb 11, 2011, at 6:14 AM, Michael Pearmain wrote:
Hi All,
Im looking for some help passing function arguments and referencing
them,
I've made a replica, less complicated function to show my problem,
and how
i've made a work around for this. However i suspect there is a _FAR_
better
way of doing this.
If i do:
BuildDecayModel <- function(x = "this", y = "that", data =
model.data) {
model <- nls(y ~ SSexp(x, y0, b), data = model.data)
return(model)
}
...
"Error in lm.fit(x, y, offset = offset, singular.ok =
singular.ok, ...) :
0 (non-NA) cases"
This function returns an error because the args are passed as "this"
and
"that" to the model, and so fails (correct?)
If i do the following:
BuildDecayModel <- function(x = "total.reach", y = "lift", data =
model.data) {
x <- data[[x]]
y <- data[[y]]
model.data <- as.data.frame(cbind(x,y))
model <- nls(y ~ SSexp(x, y0, b), data = model.data)
return(model)
}
This works for me, but it seems that i'm missing a trick with just
manipulating the args rather than making an entire new data.frame to
work
off,
The trick you are missing is how to build a formula from component
character objects. The usual approach something like this:
?formula
Perhaps:
form <- as.formula( paste(y, "~ SSexp(, " , x , ", y0, b)" ) )
(untested)
model <- nls(form, data = model.data)
paste() should result in evaluation of the argument to return "this"
and "that" which will then be bundled into a proper language object
which is not just a character string. I should say I hope this works,
but there are mysteries regarding the environment of evaluation that
continue to trip me up.
--
David.
Can anyone offer some advice?
(Some further advice: Set your client to post in plain text.)
Thanks in advance
Mike
David Winsemius, MD
West Hartford, CT
______________________________________________
[email protected] 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.
