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.
With thanks,
Ted.
--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 21-Jul-08 Time: 13:13:45
------------------------------ XFMail ------------------------------
on 07/21/2008 07:13 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.Ted, try this: plot(c(0.5,2.5), c(0.5,2.5), xlim=c(0,3), ylim=c(0,3), xaxs = "i", yaxs = "i") or perhaps this: plot(c(0.5,2.5), c(0.5,2.5), xlim=c(0,3), ylim=c(0,3), xaxs = "i", yaxs = "i", axes = FALSE, frame.plot = FALSE) axis(1) axis(2)> 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)Same thing here: plot(c(0.5,2.5), c(2.5,4.5), xlim=c(0,3), ylim=c(0,5), xaxs = "i", yaxs = "i")> 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?plot(c(0.5,2.5), c(2.5,4.5), xlim=c(0,3), ylim=c(2,5), xaxs = "i", yaxs = "i")> 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. > > With thanks, > Ted.See ?par and take note of 'xaxs' and 'yaxs', where it is noted that the default 'r' extends the axes by +/- 4% of the data range. Using 'i' gives you axes with the exact range of the data and/or the 'xlim' and 'ylim' settings. HTH, Marc Schwartz
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