On Jan 6, 2012, at 9:51 PM, R. Michael Weylandt <michael.weyla...@gmail.com
> wrote:
I imagine the answer will involve lazy evaluation and require you
use force() but I'm not quite qualified to pronounce and not at a
computer to test.
Your theory passes the experimental test:
for(i in 1:4) {force(i)
junk[[i]] <- eval(bquote(function(x){42 + .(i)*x}))}
junk
--
David.
Michael
On Jan 6, 2012, at 8:43 PM, Rolf Turner <rolf.tur...@xtra.co.nz>
wrote:
I want to create a list of functions in a for loop, with the index
of the loop appearing explicitly in the function code.
After quite a bit of thrashing around I figured out how to do it.
Here is a toy example:
junk <- vector("list",4)
for(i in 1:4) {
itmp <- i
junk[[i]] <- eval(bquote(function(x){42 + .(itmp)*x}))
}
So I'm *basically* happy, but there's something I don't understand:
Why do I need "itmp"?
That is, if I do
junk <- vector("list",4)
for(i in 1:4) {
junk[[i]] <- eval(bquote(function(x){42 + .(i)*x}))
}
then every entry of "junk" is equal to
function (x)
{
42 + 4L * x
}
i.e. I seem to get the *last* value of the index always
substituted, rather than
the "current" value. Something (subtle?) is going on that I don't
understand.
And than makes me feel not quite comfy. Can anyone enlighten me?
Ta.
cheers,
Rolf Turner
P. S. Also: Is there a *better* way of accomplishing my objective
than what I came up with?
R. T.
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David Winsemius, MD
West Hartford, CT
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