[GRASSLIST:418] Re: a huge matrix ?

[H Bowman]

> >The most straightforward approach (although not particularly
> >efficient), would be to use an iterative approach, i.e.
> >
> >	n=0
> >	last='null()'
> >	while read a1 a2 a3 a4 a5 a6 a7 a8 ; do
> >		result=pr2.pass$n
> >		r.mapcalc "$result = if (f28geo5==$a1 && f28slpcat==$a2 && f28concavity==$a3 && n_facing==$a4 && road_bas==$a5 &&str_buf==$a6 && f28f4==$a7, $a8, $last)"
> >		last=$result
> >	done < rules.txt
> >
> >where rules.txt looks like:
> >
> >	21 6 1 1 1 1 0 701.22
> >	 7 4 2 1 1 2 1 702.06
> >	...
> >
>
> Firstly I intend to try your iterative way.
> In that,  doesn't n have any increament ?
> something like n=n+1 in the loop.
> If so,Doesn't  it mean creating a new map - totally 10500 map-  in every 
> iteration

Not sure if this is what you are after, but as a general iterative bash scripting template:

n=0
r.mapcalc patchmap="null()"
while read a1 a2 a3 a4 a5 a6 a7 a8 ; do
	echo "Pass $n .."
	r.mapcalc ...
	r.patch out=patchmap in=patchmap,pr2.pass$n (?? r.mapcalc sum=sum+new ..)
	g.remove rast=pr2.pass$n
	n=`expr $n + 1`
done


actually for that n isn't needed, but still a good idea.


Hamish