On 12-04-16 1:52 PM, Paul Johnson wrote:
I'm looking for an R mentor. I want to propose a change in management
of plot options xlim and ylim.
Your suggestion sounds reasonable, but because plot limits are such a
commonly used parameter, it would have to be done quite carefully. The
questions I'd ask before implementing it are:
- Are there other locations besides plot.default where xlim and ylim
are specified? I'd like to have them updated consistently.
- Are there any conflicting uses of NA for a limit in published packages?
- Which package authors would need to be told about this change, so
they could make a compatible change?
- Where does it need to be documented?
Duncan Murdoch
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)
plot(x,y)
## 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))
range(xy$x[is.finite(xy$x)])
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!
pj
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