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Variable labels (was Re: [R] Reading SAS version 8 d ata into

2 messages · Warnes, Gregory R, Frank E Harrell Jr

Warnes, Gregory R
# 
[snip]
[snip]
Actually one of the reasons that I included the deparse(...) method was to
create a 'drop-in' substitute for the current calls to deparse(...) that are
found throughout the code and that would be backward-compatible.  Having
such a call will immensely simplify changing existing code.

It's true that the variable names don't get correctly handled once you down
a layer of function calls, but that applies AFAIK to the current
deparse(...) method  as well.
I don't think there will be a problem as long as the functions do exactly
the same thing.  To that end, perhaps we should agree on a common set of
functions and keep them in sync.  I expect that your functions are better
tested than mine, since they've been available for some time.
It seems to be a good idea to preserve the labels during subset operations.
What are the possible cons?

-Greg


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Frank E Harrell Jr
#
"Warnes, Gregory R" wrote:
Thanks for your reply Greg.
The "complex" code I was referring to was the eval()
and as.name() parts of your code.  The deparse can be
handy although I have done that on a case-by-case basis.
For example in a high-level plotting function I'll retrieve
label(an argument) and if that is empty I'll use
deparse(substitute(argument)).
Right.  That's why I try to define labels early when a data
frame is being created (e.g, in sas.get).
Mine are simple:

label <- function(x)  {
	lab<-attr(x, "label")
	if(is.null(lab))lab<-""
	lab
	}

#From Bill Dunlap, StatSci  15Mar95:

"label<-" <- if(!.SV4.) function(x, value)
  structure(x, label=value,
            class=c('labelled',
              attr(x,'class')[attr(x,'class')!='labelled'])) else
function(x, value) {    # 1Nov00 for Splus 5.x, 6.x
  attr(x,'label') <- value
  x
}

For non SV4 systems (which include R) you see above that
when putting a label on a variable a class "labelled" is
added.  This is really to handle the subsetting problem
but I would rather get rid of it if subsetting can
respect selected attributes.
If the user or a package specifies the list of attribute names
to preserve (I can only think of 'label' and 'units' right now)
I don't see a downside.  -Frank