change make_prediction() to model1() (#657)

model-basics.Rmd

@@ -214,7 +214,7 @@ These are exactly the same values we got with `optim()`! Behind the scenes `lm()
     
     ```{r}
     measure_distance <- function(mod, data) {
-      diff <- data$y - make_prediction(mod, data)
+      diff <- data$y - model1(mod, data)
       mean(abs(diff))
     }
     ```