[R-sig-Geo] Coercing multiband readGDAL objects to a matrix/vector...

[Jonathan Greenberg]

Michael:

    Thank you for your prompt reply -- if I wanted to extract multiple 
bands in a single call, how would I do that?  I suppose I could do it 
with a for-next loop, but it seems there is probably some simple way of 
doing this:

as.matrix(x[1:3]) (doesn't work, but the idea is I want bands 1-3 in this matrix).

--j




Michael Sumner wrote:
> Hello, 
>
> You can use either as.imageSpatialGridDataFrame(x[1]) or as.matrix(x[1]), 
> where "x" is a SpatialGridDataFrame or SpatialPixelsDataFrame.
>
> The "1" index assumes you want the first band, replace as appropriate. 
>
> The first gives you a list with x, y, z components in the convention
> expected by image(), so
> as.imageSpatialGridDataFrame(x[1])$z is the matrix. 
>
> The second returns the matrix directly but in a different orientation. 
>
> HTH
>
> Regards, Mike. 
>
>
> ==============Original message text===============
> On Fri, 23 Jan 2009 8:59:02 +1100 Jonathan Greenberg wrote:
>
> I was hoping I could get some info on how to coerce the type of object 
> readGDAL produces, assuming its a multiband object, into an R matrix (I 
> just want the raster values in the matrix)?  Thanks!
>
> --j
>
>