[GRASS-dev] question about the concept 'window'

Peng Du wrote:

Another question: is there any function similar to
get_map_row(…) but gets a column of data from raster image
rather than a row?

no. you'd have to load the whole map into memory for that, which
is no good for very large maps.

if you do have to do a lot of operations with full rows, and
your maps are very big, you might consider to rotate the map by
90 degrees (AFAIR there's a contrib/ module in GRASS 4 or 5 to
do that) or use r.out.mat to load the data into Matlab/Octave
whos native array layout is by rows not columns (Fortran style).
(but again they probably want to hold the whole array in memory)

Hamish

  I see.

Just out of curiosity, why is get_map_column not provided? Lack of time or some infrastructure/performance consideration?

Thanks,
Peng

On 7/19/2010 10:24 PM, Hamish wrote:

Peng Du wrote:

Another question: is there any function similar to
get_map_row(…) but gets a column of data from raster image
rather than a row?

no. you'd have to load the whole map into memory for that, which
is no good for very large maps.

if you do have to do a lot of operations with full rows, and
your maps are very big, you might consider to rotate the map by
90 degrees (AFAIR there's a contrib/ module in GRASS 4 or 5 to
do that) or use r.out.mat to load the data into Matlab/Octave
whos native array layout is by rows not columns (Fortran style).
(but again they probably want to hold the whole array in memory)

Hamish