R help - Jan 2009 - title: words in different colors?

In ?title I see the

plot(cars, main = "")
 title(main = list("Stopping Distance versus Speed", cex=1.5,
col="red",
font=3))

I can't seem to generalize this to use several colors in a single title. 
What I'd like is
in latex-ish

\red{Hair color} \black{ and } \blue{Eye color}

to serve also as an implicit legend for points that are plotted.

-Michael

-- 
Michael Friendly     Email: friendly AT yorku DOT ca 
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
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2009/1/21 Michael Friendly <friendly at yorku.ca>:
> In ?title I see the
>
> plot(cars, main = "")
> title(main = list("Stopping Distance versus Speed", cex=1.5,
col="red",
> font=3))
>
> I can't seem to generalize this to use several colors in a single
title.
 Solution from http://tolstoy.newcastle.edu.au/R/e2/help/07/09/24599.html
adapted for title:

  plot(1:10)
  title(expression("hair Color" * phantom(" and Eye
color")),col.main="red")
  title(expression(phantom("hair Color and ") * "Eye
color"),col.main="blue")
  title(expression(phantom("hair Color ") * "and" *
phantom("Eye
color"),col.main="black"))

 The trick is to overlay three titles, one for each colour, with the
stuff not in that colour wrapped in a phantom() call to produce the
correct spacing in invisible ink.

  There's probably other ways...

Barry

Michael Friendly wrote:
> In ?title I see the
>
> plot(cars, main = "")
>  title(main = list("Stopping Distance versus Speed", cex=1.5,
col="red",
> font=3))
>
> I can't seem to generalize this to use several colors in a single
title.
> What I'd like is
> in latex-ish
>
> \red{Hair color} \black{ and } \blue{Eye color}
>
> to serve also as an implicit legend for points that are plotted.
>
>   
I don't know a direct way, but you could put things together by using 
strwidth() on each piece, then plotting them at the appropriate position 
using mtext.  For example:

technicolorTitle <- function(words, colours, cex=1) {
    widths <- strwidth(words,cex=cex)
    spaces <- rep(strwidth(" ",cex=cex), length(widths)-1)
    middle <- mean(par("usr")[1:2])
    total <- sum(widths) + sum(spaces)
    start <- c(0,cumsum(widths[-length(widths)] + spaces))
    start <- start + middle - total/2
    mtext(words, 3, 1, at=start, adj=0, col=colours,cex=cex)
    }

plot(1)
technicolorTitle(c("Hair color", "and", "Eye
color"), c("red", "black",
"blue"))

(I didn't duplicate title()'s choice of position and font exactly, so 
you might want to tweak this a bit.)

Duncan Murdoch