On 7/21/2008 8:13 AM, (Ted Harding) wrote:
Hi Folks,
I've been digging for the solution to this for several
hours now. If there is a solution, it must be one of the
worst "needle-in-a-haystack" examples in R documentation!
Essentially, I want to make an x-y plot in which the
X-axis really is the X-axis (i.e. its vertical position
is at y=0), and the Y-axis really is the Y-axis (i.e.
its horizontal position is at x=0). Discussion, with
toy examples, below.
I have sort-of solved this (as stated) for one special
case, after a depth-4 search through
?plot --> ?plot.default --> ?par --> ?axis
which finally led me to the parameter "pos" to axis():
?axis
pos: the coordinate at which the axis line is to be drawn:
if not 'NA' this overrides the values of both 'line' and 'mgp[3]'.
Hence, instead of
plot(c(0.5,2.5),c(0.5,2.5),xlim=c(0,3),ylim=c(0,3),
frame.plot=FALSE)
(where the axes do not meet at the origin (0,0)), I can do
plot(c(0.5,2.5),c(0.5,2.5),xlim=c(0,3),ylim=c(0,3),
frame.plot=FALSE,pos=0)
which is *exactly* what I want in this case.
But now I want to do the same, where instead of plotting the
two points (0.5,0.5), (2.5,2.5) I want to plot (0.5,2.5), (2.5,4.5).
Provided I keep the xlim and ylim to both have lower value 0,
a similar solution again works fine:
plot(c(0.5,2.5),c(2.5,4.5),xlim=c(0,3),ylim=c(0,5),
frame.plot=FALSE,pos=0)
But, in this case, what I *really* want is to limit the Y range
to the "relevant" bit: ylim=c(2,5) -- I don't want to have a lot
of empty space below the points. So I want a Y-axis running from
y=2 to y=5, and X-axis as before from x=0 to x=3, and I want these
two axes to meet at (x=0,y=2). But how?
By analogy to the above, I need to set a "pos=0" for the X-axis,
and a "pos=2" for the y-axis. And I have not been able to discover
how to do this.
It may or may not be possible in a single call to plot(), but it is
certainly straightforward if you use separate calls to plot() and axis:
> plot(c(0.5,2.5),c(2.5,4.5),xlim=c(0,3),ylim=c(2,5), axes=F)
> axis(1, pos=2)
> axis(2, pos=0)
Generally speaking I find it is usually easier not to try to convince
plot() to do strange things: I tell it to do nothing, and do the
strange things myself.
Duncan Murdoch
______________________________________________
R-help@r-project.org 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.
