The two components of the regression-kriging model are not independent, hence
you are doing a wrong
thing if you are just summing them. You should use instead the universal
kriging variance that is
derived in gstat. The complete derivation of the Universal kriging variance is
available in
Dear David,
An other option would be to use sequential gaussian simulation. That
will allow to calculate confidence intervals in the logit scale. These
can be back-transformed into the original scale because the logit
transformation is monotone.
HTH,
Thierry
Tom,
I'm afraid things are harder than you sketch. In glm's, the parameter
estimation is done using iteratively reweighted least squares, where the
weights depend on a variance function that links the variance of
observations to the mean. So, observations (residuals) are assumed to be
Thierry,
how would you setup a Gaussian simulation such that the end result is
different from the case where these confidence intervals were directly
computed from the kriged mean and variance and a Gaussian assumption on
the errors?
--
Edzer
ONKELINX, Thierry wrote:
Dear David,
An other
Tomislav Hengl wrote:
PS: How do you back-transform the GLM prediction variance to original scale
(I was not aware of
this, apologies)? A reference would do.
1. The white book, Statistical Models in S
2. The source of predict.glm (not for the faint of heart)
3. McCullogh Nelder (I guess
Sorry, I meant UK variance of the interpolated logits.
I guess the solution is to either:
(A)
1. Run 100 SG simulations using logits;
2. Back-transform the values to 0-1 scale;
3. Determine the variance per grid node (now in 0-1 scale).
Running simulations could also be rather time-consuming
Dear list,
I have two objects of class SpatialPolygonsDataFrame
and I want to get the intersection. The first object (x)
are circles (approached as polygons) with a fake data
frame. The circles could be just in a SpatialPolygons
object, I just put the fake data frame to get the same
class as I
Try
?PolySet2SpatialPolygons
This function will bring the newly intersected polygon back to class SPDF
and then you should be able to attach the corresponding data.frame to the
new polygon object.
Andrew Niccolai
Doctoral Candidate
Yale School of Forestry
-Original Message-
From:
Thanks,
I get a problem in the inverse transform:
delme -
PolySet2SpatialPolygons(SpatialPolygons2PolySet(absUTMpolysHABS2))
Error in
PolySet2SpatialPolygons(SpatialPolygons2PolySet(absUTMpolysHABS2)) :
unknown coordinate reference system
probably because
[EMAIL PROTECTED]
CRS
