R help - Aug 2010 - How to plot an expression-label with variable text

Disclaimer: I have read plotmath, but maybe it's too late today:

How do I get the two labels to be the same:

plot.new()
lab =expression(paste("Estimated ", t[50]," from tgv"))
text(0.5,0.5,lab)
# Should look the same as above. I could not get the substitute right:
what = "tgv"
lab =expression(paste("Estimated ", t[50]," from ",what))
text(0.5,0.2,lab)


Dieter

hi,

try this

lab =bquote(paste("Estimated ", t[50]," from ",.(what)))


HTH,

baptiste

On 27 August 2010 20:19, Dieter Menne <dieter.menne at menne-biomed.de>
wrote:
>
> plot.new()
> lab =expression(paste("Estimated ", t[50]," from tgv"))
> text(0.5,0.5,lab)
> # Should look the same as above. I could not get the substitute right:
> what = "tgv"
> lab =expression(paste("Estimated ", t[50]," from
",what))
> text(0.5,0.2,lab)
>

On Aug 27, 2010, at 2:19 PM, Dieter Menne wrote:
> Disclaimer: I have read plotmath, but maybe it's too late today:
>
> How do I get the two labels to be the same:
>
> plot.new()
> lab =expression(paste("Estimated ", t[50]," from tgv"))
> text(0.5,0.5,lab)
> # Should look the same as above. I could not get the substitute right:
> what = "tgv"
> lab =expression(paste("Estimated ", t[50]," from
",what))
> text(0.5,0.2,lab)
The problem with that method (I think) is that expression protects its  
arguments to some extent. The help page wording is that it is  
"special" and does not evaluate its arguments although you seem to  
have gotten the paste() function evaluated. Try:

plot.new()
lab <- expression(paste("Estimated ", t[50]," from tgv"))
text(0.5,0.5,lab)
# Should look the same as above. I could not get the substitute right:
what <- "tgv" ; expr <- paste("Estimated t[50] from ",
what)
lab <- as.expression(expr)  # expression() does not satisfy
text(0.5,0.2,lab)

-- 
David Winsemius, MD
West Hartford, CT

Thanks to both of you. I noted that my example was over-simplified. Looks
like I need to correct the environment when nested in a function, but I have
to catch the last bus now.

Dieter


plotExp = function(what) {
  plot.new()
  lab =expression(paste("Estimated ", t[50]," from tgv"))
  text(0.5,0.5,lab)
  # Should look the same as above. Looks like I need a substitute....
  lab =bquote(paste("Estimated ", t[50]," from ",.(what)))
##<<need
environment 
  text(0.5,0.2,lab)
}
plotExp(what)

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