R help - Aug 2007 - multiple colors within same line of text

Hi, I'm interested in using mtext(), but with the option of having multiple
colors in the same line of text.

For example, creating a line of text where:

Red is red and blue is blue

How do you create a text argument that lets you do this within mtext()?

Thanks,
Andrew
MGH Cancer Center

	[[alternative HTML version deleted]]

Hi Andrew,

This is pretty clumsy but it seems to work.  I suspect
there are many better ways

x <- seq(0, 1, length=21)
plot(db)
colour <- c("red", "blue")
mytext <- c("RED", "BLUE")
mtext( mytext, at= c(2,5), side=1, col=colour)

--- Andrew Yee <andrewjyee at gmail.com> wrote:
> Hi, I'm interested in using mtext(), but with the
> option of having multiple
> colors in the same line of text.
> 
> For example, creating a line of text where:
> 
> Red is red and blue is blue
> 
> How do you create a text argument that lets you do
> this within mtext()?
> 
> Thanks,
> Andrew
> MGH Cancer Center
> 
> 	[[alternative HTML version deleted]]
> 
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>

Andrew Yee wrote:
> Hi, I'm interested in using mtext(), but with the option of having
multiple
> colors in the same line of text.
> 
> For example, creating a line of text where:
> 
> Red is red and blue is blue
> 
> How do you create a text argument that lets you do this within mtext()?
> 
You can do something like this with "text" and then use xpd=TRUE to
use
it outside the plot. I think it would be more fiddly trying to use
"mtext".

concat.text<-function(x,y,txt,col) {
  thisx<-x
  for(txtstr in 1:length(txt)) {
   text(thisx,y,txt[txtstr],col=col[txtstr],adj=0)
   thisx<-thisx+strwidth(txt[txtstr])
  }
}
plot(0,xlim=c(0,1),ylim=c(0,1),type="n")
ctext<-c("Roses are ","red, ","violets are
","purple")
concat.text(0,0.5,ctext,col=c("black","red","black","purple"))

Jim

Andrew Yee <andrewjyee <at> gmail.com> writes:
> 
> Hi, I'm interested in using mtext(), but with the option of having
multiple
> colors in the same line of text.
> 
> For example, creating a line of text where:
> 
> Red is red and blue is blue
> 
> How do you create a text argument that lets you do this within mtext()?
> 
> Thanks,
> Andrew
> MGH Cancer Center
> 

I see this thread has languished for a couple of weeks-- I'm behind in
reading
my digests but the responses I see rely on the user figuring out how wide the
text is.  I don't think we need to do that.

Instead, try using multiple calls to mtext(), passing slightly different
expression() calls as the text argument.  Make use of the phantom()
"function"
of plotmath (see ?plotmath).

Example, which you can modify to make it look prettier:

plot( 1:10)
mtext( expression( phantom( "Red" ) * " is red and " * 
  phantom( "Blue" ) * " is blue" ), side=3 )
mtext( expression( "Red" * phantom(" is red and Blue is
blue" ) ),
  side=3, col='red' )
mtext( expression( phantom( "Red is red and " ) * "Blue" * 
  phantom( " is blue" ) ), side=3, col='blue' )


It might be a fun exercise to write a function (call it multicolorText?) that
would accept an argument such as "<col='red'>Red</col>
is red and
<col='blue'>Blue</col> is blue", then do the same thing
as the three mtext calls
above...

--David Dailey
Shoreline, Washington, USA