I am using forecast package in R by Rob Hyndman. I am using the
auto.arima() function and I have various regressors.
One of my regressors is temperature values, including both negative and positive values. I only want the temperature regressor to be effective when it is below 0 and I want the other values to be ignored.
Similarly I have another regressor (Production Prognosis) which has values that are greater than 0 Ranging from 200 to 5000. I only want to use this regressor for its values below 1000.
What is the best way to do this?