I am working through the "Forecasting Using R" DataCamp course. I have completed the entire thing except for the last part of one particular exercise (link here, if you have an account), where I'm totally lost. The error help it's giving me isn't helping either. I'll put the various parts of the task down with the code I'm using to solve them:
Produce time plots of only the daily demand and maximum temperatures with facetting.
autoplot(elec[, c("Demand", "Temperature")], facets = TRUE)
Indexelecaccordingly to set up the matrix of regressors to includeMaxTempfor the maximum temperatures,MaxTempSqwhich represents the squared value of the maximum temperature, andWorkday, in that order.
xreg <- cbind(MaxTemp = elec[, "Temperature"],
MaxTempSq = elec[, "Temperature"] ^2,
Workday = elec[,"Workday"])
Fit a dynamic regression model of the demand column with ARIMA errors and call this fit.
fit <- auto.arima(elec[,"Demand"], xreg = xreg)
If the next day is a working day (indicator is 1) with maximum temperature forecast to be 20°C, what is the forecast demand? Fill out the appropriate values incbind()for thexregargument inforecast().
This is where I'm stuck. The sample code they supply looks like this:
forecast(___, xreg = cbind(___, ___, ___))
I have managed to work out that the first blank is fit, so I'm trying code that looks like this:
forecast(fit, xreg = cbind(elec[,"Workday"]==1, elec[, "Temperature"]==20, elec[,"Demand"]))
But that is giving me the error hint "Make sure to forecast the next day using the inputs given in the instructions." Which... doesn't tell me anything useful. Any ideas what I should be doing instead?
When you are forecasting ahead of time, you use new data that was not included in elec (which is the data set you used to fit your model). The new data was given to you in the question (temperature 20C and workday 1). Therefore, you do not need elec in your forecastcall. Just use the new data to forecast ahead:
forecast(fit, xreg = cbind(20, 20^2, 1))