"Hu Chen" <[EMAIL PROTECTED]> writes:
> for example, I have two sets, x and y.
> I want to draw their histograms using different colors in a graph.
> I didn't find how to do this by reading ?hist
> Thanks very much.
You can't do that because it looks horrible ;-)
Actually, you can, because plot.histogram understands add=TRUE.
However, the opaque blocks of histograms tend to obscure eachother, so
you'd rather have something like back-to-back displays (which do
exist, I believe, in some package, but I've forgotten where).
You might do it with frequency polygons (which pretty much just amount
to playing "connect the dots" with histograms). Here's a bit of code
that I had lying about; overplotting is possible by add=TRUE -- you
likely need to manually adjust the xlim and ylim, though.
freqpoly <- function(x, ..., xlab=deparse(substitute(x)), add=FALSE,
freq=FALSE) {
force(xlab)
h <- hist(x, ..., plot=FALSE)
nbin <- length(h$mids)
minb <- h$breaks[1]
maxb <- h$breaks[nbin+1]
minm <- h$mid[1]
maxm <- h$mid[nbin]
xmin <- minb - (minm - minb)
xmax <- maxb + (maxb - maxm)
x <- c(xmin,h$mid,xmax)
y <- c(0, if (freq) h$counts else h$density, 0)
if (!add)
plot(x, y, xlab=xlab, ylab= if (freq) "Frequency" else "Density",
type="o", pch=16, ...)
else
lines(x, y, type="o", pch=16, ...)
}
--
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c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
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