On second glance, while it works for 'stack', it doesn't appear to work for
'overlay':
> overlay(sapply(obs,get))
Error in function (classes, fdef, mtable) :
unable to find an inherited method for function "overlay", for signature
"list", "missing"
At this point, this may be more of a 'raster' issue for the R-Sig-Geo list...
On Nov 16, 2010, at 7:09 PM, Kevin Ummel wrote:
> Thanks, David. That does, indeed, work. It didn't occur to me that a list
> would do the job as an argument.
>
> Thanks for the fix!
>
> kevin
>
>
> On Nov 16, 2010, at 6:58 PM, David Winsemius wrote:
>
>>
>> On Nov 16, 2010, at 1:04 PM, Kevin Ummel wrote:
>>
>>> Sorry, I shouldn't have used 'sum' as an example; I am looking for a
>>> solution in the case of functions that do not result in simple vectors or
>>> matrices.
>>>
>>> The "real-world" example is something like the following using the 'raster'
>>> package, though (I think) any command producing an S4 object could be a
>>> candidate:
>>>
>>> r1 <- raster(system.file("external/test.grd", package="raster"))*1
>>> r2 <- raster(system.file("external/test.grd", package="raster"))*2
>>>
>>> obs=objects(pattern=glob2rx("r?"))
>>>
>>> #Would like to generate the equivalent of...
>>>
>>> stack(r1,r2)
>>
>> Have you tried what would seem to be the obvious generalization of the
>> example offered:
>>
>> str(stack(sapply(obs, get))) # it does not throw any error and seems to
>> have data in it
>>
>>>
>>> ...using a variation of obs as an argument to 'stack' (potentially very
>>> long).
>>
>> Also tested:
>>
>> str(
>> stack( c(sapply(obs, get),sapply(obs, get)) ) # doing a four object test
>> ) # no error
>>
>> (I did not see any indication in the help page for get that it's operation
>> was restricted to S3 objects. If there is such a restriction then warnings
>> should be added there.)
>>
>>
>>>
>>> Cheers,
>>> Kevin
>>>
>>>
>>> On Nov 16, 2010, at 5:07 PM, David Winsemius wrote:
>>>
>>>>
>>>> On Nov 16, 2010, at 10:34 AM, Kevin Ummel wrote:
>>>>
>>>>> A bit embarrassed to post this seemingly trivial question, but I can't
>>>>> find anything in the archive that's quite relevant:
>>>>>
>>>>> a1=1
>>>>> a2=2
>>>>>
>>>>> obs=objects(pattern=glob2rx("a?"))
>>>>>
>>>>> I want to utilize 'obs' as a function argument to produce something like:
>>>>>
>>>>> sum(a1,a2)
>>>>>
>>>>
>>>> ?get
>>>>> sum(sapply(obs, get))
>>>> [1] 3
>>>>
>>>>
>>>>> Obviously, sum(obs) doesn't work, but I've tried variations of 'eval',
>>>>> 'parse', 'mget', and 'noquote' without success. What am I missing?
>>>>>
>>>>> Thanks,
>>>>> Kevin
>>>>>
>>>> --
>>>> David Winsemius, MD
>>>> West Hartford, CT
>>>>
>>>
>>
>> David Winsemius, MD
>> West Hartford, CT
>>
>
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