[R] two density curves in one plot?

[Ritwik Sinha]

Hi Gabor and Dimitris,

I was wondering if this question was frequent enough to be in the R
FAQ under R Miscellanea and thought of something like this

Q. How do I plot two curves on the same graph?

A. Plot the first curve using the plot() command and add lines using
lines(). For example

d1 <- density(rnorm(100))
d2 <- density(rnorm(100))
plot(range(d1$x, d2$x), range(d1$y, d2$y), type = "n", xlab = "x",
ylab = "Density")
lines(d1, col = "red")
lines(d2, col = "blue")

Alternatively one can use points() to add points to the plot.

If you think this question should be in the FAQ and if you have any
comments/changes to the QA then I can request the maintainer of the
FAQ to include it. We could also include a lattice solution but I was
thinking of not complicating things.

Ritwik Sinha

On 8/27/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> Not sure who maintains the FAQ but its not me.
>
>
> On 8/27/06, Ritwik Sinha <ritwik.sinha at gmail.com> wrote:
> > This seems to be a common question for new commers to R, does it make sense
> > to add it to the R FAQ page? I checked it is not currently there.
> >
> > Ritwik
> >
> >
> > On 8/23/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > >
> > With lattice graphics:
> >
> > library(lattice)
> > d1 <- rnorm(100)
> > d2 <- runif(100)
> > densityplot(~ d1 + d2, auto.key = TRUE)
> >
> > On 8/23/06, Antje <niederlein-rstat at yahoo.de > wrote:
> > > Hello,
> > >
> > > I was wondering if I can plot two curves I get from "density(data)" into
> > > one plot. I want to compare both.
> > > With the following commad, I just get one curve plotted:
> > >
> > > plot( density(mydata) )
> > >
> > > Sorry for this stupid question but I could not find a solution until
> > now...
> > >
> > > Antje
> > >
> > > ______________________________________________
> > > R-help at stat.math.ethz.ch 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.
> > >
> >
> > ______________________________________________
> >
> > R-help at stat.math.ethz.ch 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.
> >
> >
> >
> >
> > --
> > Ritwik Sinha
> > Graduate Student
> > Epidemiology and Biostatistics
> > Case Western Reserve University
> >
> > http://darwin.cwru.edu/~rsinha
>



-- 
Ritwik Sinha
Graduate Student
Epidemiology and Biostatistics
Case Western Reserve University

http://darwin.cwru.edu/~rsinha