On 01/19/2011 04:04 AM, Andy Aldersley wrote:
Hello all,
Hoping that there is a fairly simple solution to my query...
I'm trying to overlay a line plot of some data onto a barplot of different
data. The y-axes are different for each set of data but the x-axes are the same
(1:12, corresponding with 12 months of observations). The problem I'm having is
that the centre of the bars and the points on line don't match up, which is
making the whole thing look untidy. I'm wondering if there is a way for me to
specify the positions of the centre of each bar on the graph. The code I have
is as follows:
xvals<- barplot(wetMeans[,i], yaxt='n', axisnames=F, xlab='', ylab='',
main=names[i], border=F, cex.main=0.7)par(new=T)plot(burnMeans[,i], yaxt='n',
xlab='', ylab='', type='b', cex=1, pch=16, lty=44, col='black', lwd=1.5)
As you can see I have suppressed the y-axis so this isn't a problem.I have also
tried using the barp function in the plotrix package. This solved the problem
of centring the bars on the graph, but when I overlay the line it seems to use
different tick points on the x-axis. Again, I'm not sure why this is but if
there is a quick fix that would be much appreciated.
library(plotrix)xvals<- barp(wetMeans[,i], xlab='', ylab='', main=names[i],
col='grey')par(new=T)plot(burnMeans[,i], yaxt='n', xlab='', ylab='', type='b',
cex=1, pch=16, lty=44, col='black', lwd=1.5)
I get the same result even if I suppress the x-axis in the plot command.
Hi Andy,
You seem to be heading in the right direction. barplot returns the
centers of the bars, and if you use the "lines" function to draw your
lines with these as the x values, you should get the lines in the
correct place.
barp centers the bars on integer values by default, and returns both the
x and y values in a list. Again, using "lines" should do what you want.
If you are trying to use "plot" to get the lines, beware, you may not
get the same plot extents unless you specify xlim= for both. If this
doesn't help, try sending some real or fake data and a sample plot.
Jim
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