[R] merge large number of raster objects

[Ben Zaitchik]

Thank you Henrik and Rolf.  My migraine just disappeared. : )

  myobjects = ls(pattern='^RH')
  dataobj = mget(myTemp,.GlobalEnv)
  map = Reduce(merge,dataobj)

did the trick.  do.call() didn't cut it for some reason . . . it 
returned an " 'x' is missing " error.  But Reduce works quite nicely for 
the rasters I'm working with.

Thanks again,
Ben

On 6/10/2011 2:06 AM, Henrik Bengtsson wrote:
> ...and ?mget for retrieving multiple objects as a list.  /Henrik
>
> On Thu, Jun 9, 2011 at 10:32 PM, Henrik Bengtsson<hb at biostat.ucsf.edu>  wrote:
>> See ?get and ?do.call.  That should be enough.
>>
>> ?Reduce may be an alternative for do.call(), but could also be less
>> memory efficient.
>>
>> My $.02
>>
>> /Henrik
>>
>> On Thu, Jun 9, 2011 at 7:57 PM, Ben Zaitchik<zaitchik at jhu.edu>  wrote:
>>> Hello,
>>>
>>> I have a large number of raster objects in memory, with names RH100, RH101,
>>> RH102, etc. (myobjects<- ls(pattern='^RH')).
>>> These rasters are sections of a continuous map, and I would like to combine
>>> them using the RasterObject merge tool in package 'raster.'
>>>
>>> Merge expects an input list of raster objects (outmap<-merge(x, y, ...),
>>> where x, y, and ... are raster objects).  I can run the command successfully
>>> if I type in every raster object that I want to merge, but this is
>>> impractical for the large number of objects I'm combining.
>>>
>>> I would like to apply merge to a list of object names defined using some
>>> kind of wildcard-based list command, but I'm struggling to find the right
>>> data types in R.
>>>
>>> Is there some way to convert a vector of strings (e.g.,
>>> as.vector(ls(pattern='^RH'))) to a vector of object names (as.names??) that
>>> could be specified as the input to the merge function?  What I'd really like
>>> to do is something like outmap<-merge(myobjects[1:40]), in order to merge
>>> the 40 raster objects, but I recognize that it might not be so simple.
>>>
>>> Advance apologies if this is already dealt with on the help list . . . I've
>>> gone in circles on wildcard, lapply, and names threads and haven't managed
>>> to get anything to work.
>>>
>>> Thank you,
>>> Ben
>>>
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