[GRASSLIST:2224] Re: trend surface analysis - New Problem

[Carlos Henrique Grohmann]

Hello.

I did as Roger said, and used

base2 <- surf.ls(2, east(G), north (G), isobase)

but then I get this error msg:

> Error in as.double.default(z) : (list) object cannot be coerced to double

How can fix it?
I tried as.double(), but get the same msg.

Thanks again

Carlos
-- 
+-------------------------------------------------+
        Carlos Henrique Grohmann - Guano  
    Geologist - MSc Student at IGc-USP - Brazil
       Linux User #89721  ICQ: 214752832
+-------------------------------------------------+


Citando Roger Bivand <Roger.Bivand at nhh.no>:

> 
> > Hello all
> >
> > I'm trying to do some trend surface analysis with GRASS data in R, but I
> > with some problems:
> >
> > 1 - when I get the raster from GRASS, surf.ls() doesn't accept it, since
> > its not in x,y,z format:
> >
> >> str(isobase)
> > List of 1
> >  $ isobases.auto: num [1:241266] 771 770 769 768 767 ...
> >>
> >
> > So, how can I change this to a format that surf.ls() understands?
> >
> 
> isobase$isobases.auto is the z argument. You can generate the x by east()
> of the object returned by gmeta(), and y by north() of this object. I'm
> not sure how well surf.ls() scales to this number of points, though.
> 
> > 2 - I'll try several degrees of surfaces, so I'll use surf.ls(), but
> > what about residuals? can I get them with residuals()?
> >
> Yes, residuals() should work. Again, scaling to this number of points is
> an issue. On the other hand, the residuals and fitted values will drop
> straight into the GRASS location.
> 
> Roger
> 
> > thanks in advance
> >
> > Carlos Grohmann
> >
> > --
> > +-------------------------------------------------+
> >         Carlos Henrique Grohmann - Guano
> >     Geologist - MSc Student at IGc-USP - Brazil
> >        Linux User #89721  ICQ: 214752832
> > +-------------------------------------------------+
> 
> 
> -- 
> Roger Bivand
> NHH, Breiviksveien 40, N-5045 Bergen, Norway
> 
> 
> 
>