Consider this dummy dataset. My real dataset with over 1000 records has scatter large and small values. I want to predict for values with NA but I get negative predictions. Is this a normal behaviour or I am missing a gam argument to force the model to predict positive values. library(mgcv) test <- data.frame(iddate=seq(as.Date("2014-01-01"), as.Date("2014-01-12"), by="days"), value=c(300,29,22,NA,128,24,15,1,3,30,NA,2)) test str(test) mod <- gam(value ~ s(as.numeric(iddate)),data=test) # Predict for values with NA's test$pred <- with(test,ifelse(is.na(value),predict(mod,test),value)) test [[alternative HTML version deleted]]
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