Error in model.frame.default: variable lengths differ
Joran suggested to first remove the NAs before running the model. Thus, I removed the NAs, run the model and obtained the residuals. When I updated model2 by inclusion of the lagged residuals, the error message did not appear again.
Remove NAs
df2<-df1[complete.cases(df1),]
Run the main model
model2<-gam(death ~ pm10 + s(trend,k=14*7)+ s(temp,k=5), data=df2, family=poisson)
Obtain residuals
resid2 <- residuals(model2,type="deviance")
Update model2 by including the lag 1 residuals
model2_1 <- update(model2,.~.+ Lag(resid2,1), na.action=na.omit)
Another thing that can cause this error is creating a model with the centering/scaling standardize function from the arm package -- m <- standardize(lm(y ~ x, data = train))
If you then try predict(m)
, you get the same error as in this question.