[R] Varying texts in expression(paste())

[Winfried Theis]

Hi,

I had a similar problem last year and Thomas Lumley helped me a lot on this. I
needed to replace some variables by their values in a quite complicated text
expression. Here is what Thomas suggested:

<quote Thomas Lumley on>
In your example you wanted b and c to be elements of a vector.  They
actually have to be elements of a list

> c(quote(beta),quote(gamma^3))
[[1]]
beta

[[2]]
gamma^3

So
 expr1<-quote(alpha)
 expr2<-c( quote(beta), quote(gamma^3))
 plot(1:10,main=substitute("Estimated "*a*" for "*b*" vs."*c,
        list(a=expr1,b=expr2[[1]],c=expr2[[2]])))

Finally, you could even make the expressions from text strings if you want
to

str1<-"alpha"
str2<-c("beta","gamma^3")

expr1<-parse(text=str1)[[1]]
expr2<-parse(text=str2)
 plot(1:10,main=substitute("Estimated "*a*" for "*b*" vs."*c,
        list(a=expr1,b=expr2[[1]],c=expr2[[2]])))

<quote Thomas Lumley off>
For full details see (and this is worthwhile!) the thread "[R] Constructing
titles from list of expressions" from August 7, 2002.

Thanks again to Thomas,

Winfried

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E-Mail: Winfried Theis <theis at statistik.uni-dortmund.de>
Date: 31-Jan-03

Dipl.-Math. Winfried Theis
SFB 475, Fachbereich Statistik, Universit"at Dortmund, 44221 Dortmund
Tel.: +49-231-755-5903 FAX: +49-231-755-4387
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