Hi Martin,
On 05/18/2015 05:14 AM, Martin Maechler wrote:
From R-help, subject "Variable number of loops"
I've opened a new thread, moving from R-help to R-devel ..
Jim Lemon
on Sun, 17 May 2015 09:19:06 +1000 writes:
> Hi all, Given the number of help requests that involve
> permutations/combinations, and the less than obvious
> naming of the expand.grid function, perhaps adding an
> alias such as "permute.elements" or "combine.elements"
> might ease the tasks of both searchers and those offering
> help. Neither of the above names appear to be used at
> present.
> Jim
Using \alias{} is not a very good thing here, since as you know they
are *key*s that must remain unique if possible and they can be
linked to -- which I think would not be helpful for 'expand.grid'.
It seems to me that Jim was maybe suggesting to define an alias for the
expand.grid function i.e. something like:
permute.elements <- expand.grid
or
combine.elements <- expand.grid
as a way to address the "less than obvious naming of the expand.grid
function". But maybe I misunderstood...
Cheers,
H.
Rather, for quite a few years now, we have had \concept{} for
adding "search keywords", i.e., things that
help.search() and hence ?? will find.
The other advantage of \concept{} is that you can use short
phrases, i.e.,
\concept{all variable combinations}
would be possible here.
(Better wording proposals for this specific case are welcome! --
maybe privately).
Martin Maechler, ETH Zurich
> On Sun, May 17, 2015 at 5:54 AM, Bert Gunter
> wrote:
>> 1. Please always reply to the list unless there is a
>> compelling reason to keep the discussion private. You
>> will have a better chance of getting something useful
>> that way.
>>
>> 2. I don't know what you mean by "I don't have a fixed
>> number of variables." You have to specify at least the
>> number of variables and how many levels each has in order
>> to work out what you requested, which is **NOT** the
>> number of permutations but the number of combinations
>> AFAICS, which is exactly what expand.grid will give you.
>>
>> 3. Maybe what you're looking for is the ... arguments in
>> function calls, which would be used along the lines of:
>>
>> myfun <- function( x,y,...) { ## some code combs <-
>> expand.grid(...) ## some more code }
>>
>> Any good R tutorial will tell you about this if this is
>> unfamiliar.
>>
>> 4. Another possibility might be to deliver a list of
>> named variables as an argument and then use do.call, e.g.
>>
>> myfun <- (x,y, alist) { ## some code combs <-
>> do.call(expand.grid, alist) ## some more code }
>>
>> ?do.call and/or a tutorial for details.
>>
>> 5. Otherwise, maybe someone else can figure out what
>> you're looking for.
>>
>> Cheers, Bert
>>
>>
>>
>> Bert Gunter Genentech Nonclinical Biostatistics (650)
>> 467-7374
>>
>> "Data is not information. Information is not
>> knowledge. And knowledge is certainly not wisdom."
>> Clifford Stoll
>>
>>
>>
>>
>> On Sat, May 16, 2015 at 11:16 AM, WRAY NICHOLAS
>> wrote:
>>> I might be but doesn't expand.grid need a defined and
>>> listed number of inputs? The problem I'm having is that
>>> the number of variables is not fixed, so I'm not sure
>>> whether I can reference the variable number of variables
>>> by using a vector -- haven't had time to try yet But
>>> thanks anyway Nick Wray
>>>
>>> On 16 May 2015 at 14:28, Bert Gunter
>>> wrote:
Are you trying to reinvent ?expand.grid ?
-- Bert
Bert Gunter Genentech Nonclinical Biostatistics (650)
467-7374
"Data is not information. Information is not
knowledge. And knowledge is certainly not wisdom."
Clifford Stoll
[...]
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