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rregressionlogistic-regressiongammgcv

offset[[i]] error when doing binary logistic regression with mgcv GAM

I'm trying to fit a generalized additive model with a binary response, using the code:

library(mgcv)
m = gam(y~s(x1)+s(x2), family=multinom(K=2), data=mydata)

Below is a part of my data (total sample size is 443) :

mydata[1:3,]
   y       x1        x2
1  1 12.55127 0.2553079
2  1 12.52029 0.2264185
3  0 12.53868 0.2183521

But I receive this error: 

Error in offset[[i]] : attempt to select less than one element

What is wrong with my code?

Solution

  • First of all, for binary response, why not use family = binomial()?

    Secondly, if you want to test multinom, set K = 1, because categories are coded from 0 to K. See ?multinom. However, you need to pass in a list of model formulae, for multinom family. Even if K = 1, you would need a length-1 list. Use list(y ~ s(x1) + s(x2)).