Eliminating predictors
You do not want to exclude the lagged coupon effect yet. The company needs a really sound model to improve it's future marketing decisions and to effectively run their campaign. To be 100% sure, you perform backward selection of predictors by using the function stepAIC(), loaded from the add-on package MASS.
The stepAIC() function builds all possible combinations of predictors and determines which has the lowest AIC. The argument direction = "backward" starts the selection process with the extended.model and sequentially removes terms in an effort to lower the AIC. The argument trace = FALSE suppresses information to be printed during the running of the selection process. The final model, resulting in the minimum AIC value, is summarized by the function summary().
Это упражнение является частью курса
Building Response Models in R
Инструкции к упражнению
- Load the add-on package
MASSby using the functionlibrary(). - Perform backward elimination of predictors on the
extended.modelobject by using the functionstepAIC(). Assign the result to an object namedfinal.model. - Summarize the
final.modelobject by using the functionsummary().
Интерактивное практическое упражнение
Попробуйте выполнить это упражнение, дополнив этот пример кода.
# Load the MASS package
# Backward elemination
final.model <- ___(___, direction = ___, trace = ___)
# Summarize the final model