[R] Combining two histograms

[Henrik Bengtsson]

If you looking for something like 

x1 <- rnorm(1000,  0.4, 0.8)
x2 <- rnorm(1000,  0.0, 1.0)
x3 <- rnorm(1000, -1.0, 1.0)
hist(x1, width=0.33, offset=0.00, col="blue", xlim=c(-4,4),
 main="Histogram of x1, x2 & x3", xlab="x1 - blue, x2 - red, x3 - green")
hist(x2, width=0.33, offset=0.33, col="red", add=TRUE)
hist(x3, width=0.33, offset=0.66, col="green", add=TRUE)

with results as in http://www.maths.lth.se/help/R/plot.histogram/ there is
an extension to hist() (actually plot.histogram()) in the R.basic package
(part of the R.classes bundle). See
http://www.maths.lth.se/help/R/R.classes/ for installation instructions.

BTW, you should also consider plotting density() estimates.

Henrik Bengtsson

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Sean Davis
> Sent: Wednesday, February 02, 2005 2:42 PM
> To: r-help
> Subject: [R] Combining two histograms
> 
> 
> I have data like:
> 
> a <- rnorm(20000)
> b <- rep(FALSE,20000)
> b[sample(1:20000,15000)] <- TRUE
> 
> Using Lattice graphics, I can produce two side-by-side 
> histograms quite 
> easily by:
> 
> histogram(a | b)
> 
> However, I would like to produce a "single" histogram with two bars 
> within each bin, one for each group, as the groups are in 
> reality very 
> slightly different from each other.  The difference isn't evident 
> unless one "overlays" the two histograms in some manner.
> 
> Thanks,
> Sean
> 
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