Hi,
It seems to me that you could write a generic function myplot() and
have different methods for each class of object (like plot does).
Either S3 or S4 classes would do I think. Then it is only a matter of
making each method work separately. In particular, the method for a
formula could contain the with(data, ) construct to make all the
variables accessible to the text() function.
HTH,
baptiste
On 4 Apr 2009, at 23:27, Derek Ogle wrote:
Sorry for posting this twice, but I still have not solved this problem
and am hoping for some assistance.
I am attempting to write a function that is flexible enough to respond
to the user providing a formula (with a data= argument) or not
(similar
to plot(x,y) versus plot(y~x,data=data)). I have found a method to
work
with this in a simple case but am having trouble determining how to
"find" a variable from within the data= argument that is not part of
the
formula. The following code illustrates (I know that
plotrix::thigmophobe.labels() does what this function does) my problem
...
myplot <- function(x,y=NULL,data=NULL,label=NULL) {
if (class(x)=="formula") {
mf <- model.frame(x,data=data)
x <- mf[,2]
y <- mf[,1]
}
if (is.null(y)) stop("Y-axis variable is missing")
plot(x,y)
if (!is.null(label)) text(x,y,label)
}
# dummy data
df <-
data
.frame(x=runif(10),y=runif(10),grp=factor(rep(c("Yes","No"),each=5))
)
# both calls work as expected
with(df,myplot(x,y))
myplot(y~x,data=df)
# only first works as I would hope
with(df,myplot(x,y,label=grp))
myplot(y~x,data=df,label=grp)
# this works but is clumsy
myplot(y~x,data=df,label=df$grp)
Any help with how to make this function recognize the "grp" variable
in
"df" when using the formula without having to type "df$grp" when
supplying it to the "label=" argument would be greatly appreciated.
Thank you in advance.
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_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
______________________________________________
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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.
