Hey Roberto! Never done it in Grass but its a typical operation.
For me it seems a bit confusing with for me since you are not showing me a glm fitting but instead just using the occurrence map in the logistic link function. What you need to do is to fit a GLM to the binary data you have, something you can do in R for example check here: http://www.statmethods.net/advstats/glm.html Then you will build your output in grass using the r.mapcalc: F(x) = 1 / ( 1+ e^(-GLM) (That will be your probability map). But, you can actually do everything using R only, no need to come into grass but you can if you want. Good luck! Ciao! On 5 September 2014 10:46, Roberto Marzocchi <[email protected]> wrote: > Dear all, > > I have dichotomous data (occurrence 1 and non-occurence 0) and I want to > use the logistic regression method in order to obtain susceptibility map > of landslide occurrence. > > I try to use r.regression.multi, but I am not sure to correctly define the > mapy variable.. > > I try to use r.mapcalc > > *r.mapcalc > expression="logit_occurrence=log(occurrence_map+0.00001)-log(1-occurrence_map+0.00001)"* > > obtaining a map that go from -11.5 (not occurrence) to +11.5 (occurrence) > > when I try to use r.regression.multi I obtain a lot of null values in > residuals and estimates map. > > i do not understand why.. > > Thanks in advanced for the attention > Roberto > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > -- Nuno César de Sá +351 91 961 90 37
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