[R] plot changes usr?

[Jim Lemon]

Hi Ed,
While David's suggestion is correct, the change in par("usr") results from
your resetting the plot limits.

data(mtcars)
plot(mtcars$mpg, mtcars$hp)
par("usr")
[1]   9.46  34.84  40.68 346.32
par(new=TRUE)
plot(mtcars$mpg, mtcars$hp,col="red",axes=FALSE)
par("usr")
[1]   9.46  34.84  40.68 346.32

Jim

On Tue, Sep 29, 2015 at 10:57 AM, David Winsemius <dwinsemius at comcast.net>
wrote:

>
> On Sep 28, 2015, at 5:33 PM, Ed Siefker wrote:
>
> > I'm trying to plot() over an existing plot() like this:
> >
> >> attach(mtcars)
> >> plot(mpg, hp)
> >> par(new=TRUE)
> >> par("usr")
> > [1]   9.46  34.84  40.68 346.32
> >> plot(mpg, hp, col="red", axes=FALSE, xlim=par("usr")[1:2],
> ylim=par("usr")[3:4], xlab="", ylab="")
> >> par("usr")
> > [1]   8.4448  35.8552  28.4544 358.5456
>
> The default usr ranges are some factor (my hazy memory says 104%) of the
> range of thex- and y-values unless you specify otherwise. This choice
> allows round data-points to be displayed at the extremes. Why are you
> trying to muck with the plot setup? The right way would be to use points().
>
>
> >
> > For some reason "usr" is changing, and so it's not plotting over the
> > existing data in the right place.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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.
>
> David Winsemius
> Alameda, CA, USA
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>

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