[GRASS5] r.mapcalc question

[David Piasecki]

When I tried running r.patch, it took a really long time. Since I'd 
never used r.mapcalc before, I thought it might be faster. The line I 
wrote in r.mapcalc seems to be checking if a pixel is null, then 
finding the image with that pixel and drawing it. I assumed r.patch was 
writing all pixels from every image every time. If it's not any faster, 
then yes, I might as well use r.patch.

Although my r.mapcalc line worked the first time, I have yet to be able 
to repeat it. For some reason, the region information changes to the 
(x,y) projection, and then I assume it's attempting to draw someplace 
else. So I may end up returning to r.patch anyway.

David


On Feb 2, 2005, at 5:26 PM, Hamish wrote:

>> Perhaps this isn't quite the fastest method, but it works. If anyone
>> knows of a more efficient way of doing the same thing, I'd be
>> interested in taking suggestions.
>
>
> so what is wrong with r.patch exactly? If it does what you want it's a
> bit less prone to user error than r.mapcalc and in theory it should
> cycle through the raster cells at about the same speed?
>
> r.patch can take a couple hundred input maps at once (in preferential 
> order).
>
>
>
> Hamish