[GRASS5] region growing - r.mapcalc bug?

[Jachym Cepicky]

On Wed, Mar 02, 2005 at 10:06:47AM +0000, Paul Kelly wrote:
> On Wed, 2 Mar 2005, Jachym Cepicky wrote:
> 
> >sorry, I need
> >if(seed[-1,-1] && (raster[-1,-1]> raster[1,1]),seed[-1,-1]+1,\
> >    if(seed[-1,0]  && (raster[-1,0] > raster[1,0]),seed[-1,-1]+1,\
> >    if(seed[-1,1]  && (raster[-1,1] > raster[1,-1]),seed[-1,1]+1,\
> >    if(seed[0,-1]  && (raster[0,-1] > raster[0,1]),seed[0,-1]+1,\
> >    if(seed[0,1]   && (raster[0,1]  > raster[0,-1]),seed[0,1]+1,\
> >    if(seed[1,-1]  && (raster[1,-1] > raster[-1,1]),seed[1,-1]+1,\
> >    if(seed[1,0]   && (raster[1,0]  > raster[-1,0]),seed[1,0]+1,\
> >    if(seed[1,1]   && (raster[1,1]  > 
> >    raster[-1,-1]),seed[1,1]+1,null()))))))))
> 
> Have you tried the isnull() function in r.mapcalc? That old tutorial you 
> linked to was written for GRASS 4 where there was no null cell concept.
> 
> Paul

Dou you mean something like
rg = \
     if(!isnull(seed[-1,-1]) && (raster[-1,-1]> raster[1,1]),1,\
     if(!isnull(seed[-1,0] ) && (raster[-1,0] > raster[1,0]),1,\
     if(!isnull(seed[-1,1] ) && (raster[-1,1] > raster[1,-1]),1,\
     if(!isnull(seed[0,-1] ) && (raster[0,-1] > raster[0,1]),1,\
     if(!isnull(seed[0,1]  ) && (raster[0,1]  > raster[0,-1]),1,\
     if(!isnull(seed[1,-1] ) && (raster[1,-1] > raster[-1,1]),1,\
     if(!isnull(seed[1,0]  ) && (raster[1,0]  > raster[-1,0]),1,\
     if(!isnull(seed[1,1]  ) && (raster[1,1]  > raster[-1,-1]),1,null()))))))))

??

But I need to detect neighbourhood of the central point, if it is
"notnull()"...

OOh, I have it: 
    if(x) = TRUE if x != 0, but
    if(x) = TRUE if isnull(x) 

(I hope, you can understand).

Now I run
    rg = \
     if(seed, 1, \
     if(seed[-1,-1] && (raster[-1,-1]> raster[1,1]),1,\
     if(seed[-1,0]  && (raster[-1,0] > raster[1,0]),1,\
     if(seed[-1,1]  && (raster[-1,1] > raster[1,-1]),1,\
     if(seed[0,-1]  && (raster[0,-1] > raster[0,1]),1,\
     if(seed[0,1]   && (raster[0,1]  > raster[0,-1]),1,\
     if(seed[1,-1]  && (raster[1,-1] > raster[-1,1]),1,\
     if(seed[1,0]   && (raster[1,0]  > raster[-1,0]),1,\
     if(seed[1,1]   && (raster[1,1]  > raster[-1,-1]),1,\
     0)))))))))

where seed is map containing 1 and 0 but NOT null values. Now it works fine.


it is in xif.c file:
/********************************************************************
 if(a)        1,0,1  1 if a is non zero, 0 otherwise
 if(a,b)      b,0,b  b if a is non zero, 0 otherwise
 if(a,b,c)    b,c,b  b if a is non zero, c otherwise
 if(a,b,c,d)  d,c,b  b if a is positive, c if a is zero, d if a is negative
********************************************************************/

should be

/********************************************************************
 if(a)        1,0|null,1  1 if a is non zero AND not null, null otherwise
...

But I don't know, how to corect it...

Jachym
-- 
Jachym Cepicky
e-mail: jachym.cepicky at centrum.cz
URL: http://les-ejk.cz
GPG: http://www.fle.czu.cz/~jachym/gnupg_public_key/