[R] basic question about changing limits on generated plots

[Marc Schwartz]

On Wed, 2005-02-23 at 17:42 -0500, rif wrote:
> Is it possible to change the limits on plots that are already on the
> screen?  In particular, is there any R equivalent to the sequence of
> matlab commands
> 
> plot(1:10,1:10)
> hold on
> plot(2:12,5:15)
> 
> I know I can use points and lines to add points and lines to plots,
> but the limits of the plot do not change when I do this.
> 
> Looking at various examples, it seems that the answer is "no", but I
> wanted to make sure.  This seems to make exploratory data analysis
> somewhat more challenging.
> 
> It also seems like it would be plausible to write a package on top of
> the standard graphics functions that keeps track of what you've done
> and automatically replots.  Which makes me think, has someone already
> done this?
> 
> Cheers,
> 
> rif

I have not used Matlab, but I suspect that you want to use:

par(new = TRUE)

For example:

> plot(1:10,1:10)

# Check plot region limits
> par("usr")
[1]  0.64 10.36  0.64 10.36

# Set par("new") to not overwrite existing plot
> par(new = TRUE)

> plot(2:12,5:15)

# Re-check plot region limits
> par("usr")
[1]  1.6 12.4  4.6 15.4

See ?par for more information.

Note also that par("usr") is not read-only, so you can explicitly change
it when required:

> plot(1:10,1:10)

> par("usr")
[1]  0.64 10.36  0.64 10.36

# Now reset the plot region limits
> par(usr = c(0, 20, 0, 20))

# Check it
> par("usr")
[1]  0 20  0 20


You do not indicate what OS you are using, but Under Windows, there is
an ability to record plots. See R Windows FAQ 4.2. Otherwise, save the R
code that you use to generate the plot and either C&P it or source() it
or use ESS.

HTH,

Marc Schwartz