Exercise

Manually calculating predictions with interactions

In order to understand how predict() works, it's time to calculate the predictions manually again. For this model, there are three separate lines to calculate for, and in each one, the prediction is an intercept plus a slope times the numeric explanatory value. The tricky part is getting the right intercept and the right slope for each case.

mdl_price_vs_both_inter and explanatory_data are available; dplyr and tidyr are available.

Instructions 1/2

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  • Get the coefficients from mdl_price_vs_both_inter, assigning to coeffs.
  • Get the three intercept coefficients from coeffs, assigning to intercept_0_15, intercept_15_30, and intercept_30_45.
  • Get the three slope coefficients from coeffs, assigning to slope_0_15, slope_15_30, and slope_30_45.