CODEWITHSUNDEEP
rlegend
DatamineR
DatamineR

Reputation: 9628

Insert the value of an argument into the legend

I am trying to write a function with a graph-output. I would like to insert a legend with a value of the argument.

For example:

f<-function(x,alpha=0.9){
   ....
   plot(x)
   legend("topleft",expression(alpha)???)
   }

'expression(alpha)' should equal the current value of alpha.

Can anyone tell me how I can do it?

Upvotes: 0

Views: 224

Answers (1)

IRTFM
IRTFM

Reputation: 263451

I don't see a test case yet, but the usual answer to this sort of question (where one portion of an expression needs to be evaluated) is bquote with its built-in .() function:

f<-function(x,alpha=0.9){ .... plot(x) legend("topleft", bquote(.(alpha)) ) }

The `.() function isolates the section(s) that deserve evaluation. See also the plotmath page:

?plotmath

Sometimes substitute is needed:

 alpha=0.2
 substitute( alpha, list(alpha=alpha) )
 #0.2

.... but most people find bquote easier to work with.

The addtional code requested with some editing to avoid overwriting label1:

x<-seq(0,60,length=150) 
 y<-rnorm(150,0,10) 
 yy<-x+y 
 d<-cbind(x,yy) 
 m<-lm(d[,2]~d[,1]) 
 plot(x,yy) > abline(m) 
 label1<-summary(m)$'r.squared' 
 label2<-summary(m)$'adj.r.squared' 
 legend("topleft", legend=bquote( R^2==.(label1)*";"~Adj.R^2==.(label2) ) )

Upvotes: 1

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