[R] altering a "call" variable from quote()

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Jack Tanner
> Sent: Sunday, March 27, 2011 9:14 PM
> To: r-help at stat.math.ethz.ch
> Subject: Re: [R] altering a "call" variable from quote()
> 
> Jack Tanner <ihok <at> hotmail.com> writes:
> 
> > > b = quote(b==3)
> > 
> > Now I want to append "&& x > 2" to the value of b. How do I do that?
> 
> Never mind, I figured it out:
> 
> substitute(b && x > 2, list(b=b))

You can also use call() or as.call(): 
  > e1 <- substitute(b && x > 2, list(b=b))
  > e2 <- call("&&", b, quote(x>2))
  > e3 <- as.call(list(quote(`&&`), b, quote(x>2)))
  > identical(e1,e2) && identical(e1,e3)
  [1] TRUE
substitute can be a pain when the first argument is not
a literal expression.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> 
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