Errata for R 2nd Edition SECOND Print

Correction

"...positive errors (under-forecasts) than negative errors (over-forecasts)"

Replace 365.25 with 365 in second line of code to obtain the bottom panel of Figure 5.8 (following a change in the stlm() function)

The forecasted residual for April 2001 is computed by plugging in the most recent mean-centered residual from March 2001 (equal to 12.108 - 0.3728) into the AR(1) model: 0.3728 + (0.5998)(12.108 - 0.3728) = 7.411. The positive value tells us that the regression model will produce a ridership forecast for April 2001 that is too low and that we should adjust it up by adding 7,411 riders... the improved two-stage model [regression + AR(1) correction] corrected it by increasing it to 2,011,682 riders.