# [Rd] subset() wish: allow "select" for non-dataframes

**Martin Maechler
**
Martin Maechler <maechler@stat.math.ethz.ch>

*Tue, 26 Sep 2000 21:52:47 +0200*

{Mainly to the author of the subset() function,
but RFC to all "R-develers": }
Wouldn't it be worth redefining subset.default() such
that `anything reasonable' would allow a select argument?
Currently, only subset.data.frame() allows a select argument,
and hence we can have
> (x <- c(a=1, b=3, d= 7:10))
a b d1 d2 d3 d4
1 3 7 8 9 10
> subset(as.data.frame(rbind(x)), select = -(d2:d3))
a b d1 d4
x 1 3 7 10
{and ``subset(as.data.frame(rbind(x)))'' might already be a sensible
definition for subset.default at least
if(!missing(select) && !is.null(names(x)));
and similarly for matrices.
}
---
Using ranges and "-" in indices for names instead of just integers
is a feature that I have been missing for a long time.
It would allow much more expressive code in some situations.
2nd thought:
One could even start thinking if we should n't even enhance
"[" and "[[" instead of just subset()...
I agree that one might not like things like x[- d1] that are
undefined when not part of the index, but then
"i , j" is also not really defined when not inside "[ .. ]" ...
--
[Evening musings; maybe I'm too close to dream already...]
Martin
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