merge large number of raster objects

...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