Re: [R] passing a variable (containing the value of the argument) to a function

[Spencer Graves]

Hi, Peter:  I'll have to study your example and alternatives.  spencer 
graves

Peter Dalgaard wrote:

Spencer Graves <[EMAIL PROTECTED]> writes:

 

Hi, Peter:     How does that compare with the following: for (myname
in names(myframe)[1:4]){
 mdl <- formula(paste(myname, "~ etc.etc"))
 myfit <- lm(mdl, data=myframe)
 print(summary(myfit))
}
     Or: for (myname in names(myframe)[1:4]){
 lm.txt <- paste("lm(", myname, "~ etc.etc, data=myframe)")
  myfit <- eval(parse(text=lm.txt))
 print(summary(myfit))
}
     You are teaching me new uses of "substitute", and I just wonder
about the relative advantages and disadvantages of the different
approaches.     Thanks,
     spencer graves
   

Those variants should work (and similar code is all over the place in
the modelling functions). I just tend to prefer to avoid going via the
textual representation. There are a couple of devils lurking in there,
in particular if a data frame has variables with "funny names" -
spaces or special characters inside, for example.
To wit:

 

myname <- "foo bar"
lm.txt <- paste("lm(", myname, "~ etc.etc, data=myframe)")
lm.txt
   

[1] "lm( foo bar ~ etc.etc, data=myframe)"
 

parse(text=lm.txt)
   

Error in parse(file, n, text, prompt) : parse error

 

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