[R-sig-Geo] [Fwd: v.reclass]

[Agustin Lobo]

-------- Original Message --------
Subject: 	v.reclass
Date: 	Tue, 15 Sep 2009 14:40:28 +0200
From: 	Agustin Lobo <alobolistas at gmail.com>
To: 	grass-stats at lists.osgeo.org



Hi again,

As a result of an R process, I have to reclassify
the input vector layer. Normally, I would do it
in R, but as the vector is huge, I prefer making the
rules file in R and use v.reclass in grass.

My goal is to reclassify field VALUE of vector Montseny07 according
to a table generated in R:
> b3rec[1:3,]
    v         
[1,] "18"  "274"
[2,] "22"  "274"
[3,] "117" "274

so that VALUE 18 would become 274 and so on.

I've made the following in R to create the rules file:
z <- file("delme.txt", "w")
for (i in 1:nrow(b3rec)){
   writeLines(text=paste("VALUE",b3rec[i,2]), con = z, sep = "\n")
   writeLines(text=paste("WHERE VALUE=",b3rec[i,1],sep=""), con=z, sep 
= "\n")
}
close(z)

which creates a file delme.txt such as:
VALUE 274
WHERE VALUE=18
VALUE 274
WHERE VALUE=22
VALUE 274
WHERE VALUE=117
VALUE 274
WHERE VALUE=146
...

My understanding of this rules file was that
where we had VALUE 18, we would have VALUE 274
Nevertheless, when I run v.reclass, I get an error:

> system("v.reclass Montseny07 rules=delme.txt out=Monstseny07b3rec")
ERROR: Unknown rule option: 'VALUE'

So I remade the rules files using
cat 274
WHERE VALUE=18
etc

but then I get a vector object with a table with only one field cat. I 
would prefer
having the same table as in the original vector, just with some of the 
values
in field VALUE modified according to the rules file. Is there a way of 
doing that?

Also, is there the equivalent to "* = *" in r.reclass to get the rest
of values unchanged?

Thanks!

Agus


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