[R] seeking help with with()

[Simon Fear]

I tried to define a function like:

fnx <- function(x, by.vars=Month)
  print(by(x, by.vars, summary))

But this doesn't work (does not find x$Month; unlike other functions,
such as
subset(), the INDICES argument to "by" does not look for variables in
dataset
x. Is fully documented, but I forget every time). So I tried using
"with":

fnxx <- function(x, by.vars=Month)
  print(with(x, by(x, by.vars, summary)))

Still fails to find object x$Month. 

I DO have a working solution (below) - this post is just to ask: Can
anyone
explain what happened to the with()?



FYI solutions are to call like this:

fnx(airquality, airquality$Month)

but this will not work generically - e.g. in my real application the
dataset
gets subsetted and by.vars needs to refer to the subsets. So redefine
like
this:

fny <- function(x, by.vars=Month) {
  attach(x)
  print(by(x, by.vars, summary))
  detach(x)
}
 

Simon Fear
Senior Statistician
Syne qua non Ltd
Tel: +44 (0) 1379 644449
Fax: +44 (0) 1379 644445
email: Simon.Fear at synequanon.com
web: http://www.synequanon.com
 
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