Hello all, In trying a spatial model with spatstat I am running into a conceptual problem. It might be more of a general modelling doubt than a specific spatial problem, but I hope someone can help.
I am running a ppm() model that includes two covariates (as pixel images), one is primary productivity at sea, and the other is distance to a point that is not included in the pattern window. That means there is no 0 value, the range of values goes from 400 to 1400 approx. When I run the model and look at the var-covar matrix using 'vcov(model, what = "corr")' , there is a very strong correlation (around -0.85) between the intercept and this covariate. I am not sure that this is a problem, but I have tried a couple of things just in case: 1/ centering the covariate values around the mean just changes the sign of the correlation (from -0.85 to +0.85 approx). 2/ normalizing the covariate values, so the values go from 0 to 1 makes the correlation between this covariate and the intercept almost 1 (0.99) It also makes the effect of this covariate three orders of magnitude higher than the effect of the other covariate, which didn't happen before and was not expected from the data. Any advice? Thanks in advance! Virginia Morera PhD Student Department of Animal Biology University of Barcelona Aquest correu electrònic i els annexos poden contenir informació confidencial o protegida legalment i està adreçat exclusivament a la persona o entitat destinatària. Si no sou el destinatari final o la persona encarregada de rebre’l, no esteu autoritzat a llegir-lo, retenir-lo, modificar-lo, distribuir-lo, copiar-lo ni a revelar-ne el contingut. Si heu rebut aquest correu electrònic per error, us preguem que n’informeu al remitent i que elimineu del sistema el missatge i el material annex que pugui contenir. Gràcies per la vostra col·laboració. Este correo electrónico y sus anexos pueden contener información confidencial o legalmente protegida y está exclusivamente dirigido a la persona o entidad destinataria. Si usted no es el destinatario final o la persona encargada de recibirlo, no está autorizado a leerlo, retenerlo, modificarlo, distribuirlo, copiarlo ni a revelar su contenido. Si ha recibido este mensaje electrónico por error, le rogamos que informe al remitente y elimine del sistema el mensaje y el material anexo que pueda contener. Gracias por su colaboración. This email message and any documents attached to it may contain confidential or legally protected material and are intended solely for the use of the individual or organization to whom they are addressed. We remind you that if you are not the intended recipient of this email message or the person responsible for processing it, then you are not authorized to read, save, modify, send, copy or disclose any of its contents. If you have received this email message by mistake, we kindly ask you to inform the sender of this and to eliminate both the message and any attachments it carries from your account.Thank you for your collaboration. [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo