On 01/12/2011 1:12 PM, jcano wrote:
Hi all
How can I change the limits (xlim or ylim) in a plot that has been already
created?
You can't, if you're using classic R graphics. They use an "ink on
paper" model of graphics. If you want to change what you've drawn, you
get a new piece of paper.
Your two solutions below are the usual methods to work around this
limitation. The first is the easiest method in general, though it's
not particularly easy if you're using curve(). Generally if you're
planning to plot y1 vs x1 and y2 vs x2, you can set your ylim to
range(c(y1, y2)) and your xlim to range(c(x1, x2)) and things are fine.
If you want to follow this strategy with curve(), you need to call it
twice for each curve: once to find the range of points it would plot
(they are in the return value of the function), and a second time to
redo the plot with the calculated xlim and ylim.
Duncan Murdoch
For example, consider this naive example
curve(dbeta(x,2,4))
curve(dbeta(x,8,13),add=T,col=2)
When adding the second curve, it goes off the original limits computed by R
for the first graph, which are roughly, c(0,2.1)
I know two obvious solutions for this, which are:
1) passing a sufficiently large parameter e.g. ylim=c(0,4) to the first
graphic
curve(dbeta(x,2,4),ylim=c(0,4))
curve(dbeta(x,8,13),add=T,col=2)
or
2) switch the order in which I plot the curves
curve(dbeta(x,8,13),col=2)
curve(dbeta(x,2,4),add=T)
but I guess if there is any way of adjusting the limits of the graphic "a
posteriori", once you have a plot with the undesired limits, forcing R to
redraw it with the new limits, but without having to execute again the
"curve" commands
Hope I made myself clear
Best regards and thank you very much in advance
--
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