On 13-03-01 12:57 PM, Duncan Murdoch wrote:
On 01/03/2013 11:20 AM, William Dunlap wrote:
A core R function that fails with odd names is reformulate():
> reformulate(c("P/E", "% Growth"), response="+-")
Error in parse(text = termtext) : <text>:1:16: unexpected input
1: response ~ P/E+% Growth
^
Thanks. That one looks relatively easy to fix.
After taking a closer look, I realized that it is actually behaving as
designed. The first input to reformulate is supposed to be a character
vector, not bits of R language. For example, we want
reformulate("x*w")
to return
~ x*w
not
~ `x*w`
So you might think your example should have been entered as
reformulate(c("`P/E`", "`% Growth`"), response="`+-`")
However, this doesn't quite work: it ends up with response having
double backticks. The way to get what you want is to use
reformulate(c("`P/E`", "`% Growth`"), response=as.name("+-"))
Definitely not my favourite design for a function, but I think it's not
a code issue. Maybe something should be added to the help page, but
this is such an obscure issue that I'm not sure I could make things clearer.
Duncan Murdoch
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