Dear users; 
 
I am doing GLMs with the Gamma distribution, and I always get errors ("no valid set of coefficients: please supply starting values") or warnings ("NaNs produced in log(x)") when I use the links identity or inverse, but I don“t get them if I use the log link.
 
For example:
 
> summary(step(glm(formula=acin.x~Canais+Hetero+Indrel+Penetra+Ph2o+Pmatorg+Vasa+Aguasup+Prof+Conchdisp+Conchaglom+Ostdisp+Ostaglom+
Rugos+distcanais+distcosta+distsalina+disturbano+distsapal+cota,family=Gamma(link="inverse"))))Start:  AIC=9.18acin.x ~ Canais + Hetero + Indrel + Penetra + Ph2o + Pmatorg +     Vasa + Aguasup + Prof + Conchdisp + Conchaglom + Ostdisp +     Ostaglom + Rugos + distcanais + distcosta + distsalina +     disturbano + distsapal + cota
Error: no valid set of coefficients has been found: please supply starting valuesIn addition: Warning message:NaNs produced in: log(x) 
 
I am doing this to twelve species and I always get the errors with links identity and inverse, and never with log link.
 
Could someone give me an explanation about what is happening?
 
Thank you very much in advance!
 
Best wishes;
 
Catarina
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