On 12-01-22 3:23 PM, Ian Robertson wrote:
I am hoping someone can give me a couple of pointers on how to pass
arguments using "..."--in this specific case in an attempt to plot an
object created by ca(), a tool for correspondence analysis.
#some illustrative code
library(ca)
set.seed(123)
dat1<- data.frame(matrix(ceiling(runif(30, 1, 100)), nc=5)) #some fake data
ca1<- ca(dat1) #the correspondence analysis
plot(ca1) #basic symmetric plot
plot(ca1, ylim=c(-.4, .5), cex=2, xlab="CA Axis 1") #failed attempt to
control various "extra" parameters
title(xlab="CA Axis 1") #this gets me access to xlabels...
?plot.ca #help!
The last line suggests that "..." can be used to pass on arguments to
plot (and points), but I can't seem to make it work. I have in the past
been able to pass arguments to various tools (such plotting tools in the
lattice library) using list(), but I can't get anything similar to work
in this case. I have done some searching in the help archives (and
various of my R books) without identifying anything helpful--so any
suggestions for specific code I might try, or things I need to go read,
etc., would be much appreciated.
Reading the source to plot.ca will help. You can get it from the source
to the ca package, or get a deparsed version as ca:::plot.ca. There I
see that it passes ... to plot(), but it forces the xlab, ylab, and asp
parameters to specific values. (The labels are blanks, so using title
is a viable solution.)
The cex argument is not used by plot, it is used by points(), and
plot.ca gets the value from local variables cex.x and cex.y. So you are
probably out of luck in that case, other than asking the maintainer to
modify the function, or modifying it yourself. (You'd get a copy using
plot.ca <- ca:::plot.ca
then could use fix() to edit it. R will use yours in preference to the
original if you call it from the top level, but functions in the ca
package will continue to see the original one first.)
Duncan Murdoch
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