Using ordered probit model, I get errors from dwt and bptest.

dwt:

Error in durbinWatsonTest.default(...) : requires vector of residuals

bptest:
Error in storage.mode(y) <- "double" :
  invalid to change the storage mode of a factor

I imagine I have to restate as an individual probit model for each category,
but is there an easier way?

thanks,
bp

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