[Rd] I wish xlim=c(0, NA) would work. How about I send you a patch?

Paul Johnson pauljohn32 at gmail.com
Mon Apr 16 19:52:30 CEST 2012

I'm looking for an R mentor.  I want to propose a change in management
of plot options xlim and ylim.

Did you ever want to change one coordinate in xlim or ylim? It happens
to me all the time.

x <- rnorm(100, m=5, s=1)
y <- rnorm(100, m=6, s=1)

## Oh, I want the "y axis" to show above x=0.

plot(x,y, xlim=c(0, ))

##Output: Error in c(0, ) : argument 2 is empty

 plot(x,y, xlim=c(0,NA ))
## Output: Error in plot.window(...) : need finite 'xlim' values

I wish that plot would let me supply just the min (or max) and then
calculate the other value where needed.
It is a little bit tedious for the user to do that for herself.  The
user must be knowledgeable enough to know where the maximum (MAX) is
supposed to be, and then supply xlim=c(0, MAX). I can't see any reason
for insisting users have that deeper understanding of how R calculates
ranges for plots.

Suppose the user is allowed to supply NA to signal R should fill in the blanks.

plot(x,y, xlim=c(0, NA))

In plot.default now, I find this code to manage xlim

   xlim <- if (is.null(xlim))

And I would change it to be something like
   ##get default range
   nxlim <- range(xy$x[is.finite(xy$x)])

   ## if xlim is NULL, so same as current
    xlim <- if (is.null(xlim)) nxlim
## Otherwise, replace NAs in xlim with values from nxlim
    else xlim[ is.na(xlim) ] <- nxlim[ is.na(xlim) ]

Who is the responsible party for plot.default.  How about it?

Think of how much happier users would be!

Paul E. Johnson
Professor, Political Science    Assoc. Director
1541 Lilac Lane, Room 504     Center for Research Methods
University of Kansas               University of Kansas
http://pj.freefaculty.org            http://quant.ku.edu

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