On 4/2/2008 4:11 PM, Paul Johnson wrote:
I'm using R-2.6.2 on Fedora Linux 9.
I've been experimenting with plotmath.
I wish it were easier to combine expressions in plotmath with values
from the R program itself. There are two parameters in the following
example, the mean mymean and standard deviation mystd. I am able
to use bquote to write elements into the graph title like
mu = mymean
and R will plot the symbol mu and the value of mymean from the
program. But I want to combine that result in a string along with
other results.
Can I combine to result like this
Normal( mu = mymean , sigma = mystd)
Where symbols mu and sigma are replaced with Greek and mymean and
mystd are drawn from program?
### Filename: Normal1_2008.R
### Paul Johnson March 31, 2008
### This code should be available somewhere in
http://pj.freefaculty.org. If it is not
### email me [EMAIL PROTECTED]
mymean - 0
mystd - 1.5
myx - seq( mymean - 3*mystd, mymean+ 3*mystd, length.out=500)
myDensity - dnorm(myx,mean=mymean,sd=mystd)
## This works
plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density ,
main=expression(mu == 0))
## This works
plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density ,
main=expression(sigma == 1.5))
## This works
t1 - bquote( mu== .(mymean))
plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density , main=
t1 )
## This works
t2 - bquote( sigma== .(mystd))
plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density , main=t2)
## Can't figure how to combine t1 and t2 into plot title
### This fails!
### plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density
, main=paste( t1,t2) )
The reason it fails is that you're trying to use paste on expressions:
paste works on character strings. plotmath() uses paste formally in
expressions, but you're actually calling it. So you want to put
together an expression containing paste.
I'd do it by creating the whole title at once, e.g.
t1t2 - bquote( paste(mu== .(mymean), ' ', sigma== .(mystd)) )
and use t1t2 as the title, but you can build it out of existing
expressions too, like this:
t1t2 - bquote( paste( .(t1), ' ', .(t2) ) )
plot(myx, myDensity, type=n, xlab=X, ylab=Probability Density , main=
t1 )
## Can drop sigma in as margin text, though, on side 3.
mtext(t2, 3)
lines(myx,myDensity,lty=4, col=4) ### change line type color if you want
Supposing there is a way to do this, could I submit a working example
to be added to the help page for plotmath ? How could I go about
that?
First, put it together, then get agreement (in the R-devel list) from an
R core member that it would be a good addition. Then (depending on the
R core member), you might be asked to edit it into the plotmath man page
source
https://svn.r-project.org/R/trunk/src/library/grDevices/man/plotmath.Rd
or they might just put it in themselves.
Duncan Murdoch
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