improve descriptors examples

Initially switched from iris to mtcars, but the Orange data is a bit more interesting / illustrative.

Author: simonpcouch

R/descriptors.R

@@ -26,28 +26,28 @@
 #'   column, `..y`.
 #'   }
 #'
-#' For example, if you use the model formula `mpg ~ .` with the `mtcars`
-#'  data, the values would be
+#' For example, if you use the model formula `circumference ~ .` with the
+#' built-in `Orange` data, the values would be
 #' \preformatted{
-#'  .preds() =   10          (the 10 columns in `mtcars`)
-#'  .cols()  =   10          (10 numeric columns + 0 from dummy variables)
-#'  .obs()   = 32
+#'  .preds() =   2          (the 2 remaining columns in `Orange`)
+#'  .cols()  =   5          (1 numeric column + 4 from Tree dummy variables)
+#'  .obs()   = 35
 #'  .lvls()  =  NA          (no factor outcome)
-#'  .facts() =   0          (no factor outcome)
-#'  .y()     = <vector>     (mpg as a vector)
-#'  .x()     = <data.frame> (The other 10 columns as a data frame)
+#'  .facts() =   1          (the Tree predictor)
+#'  .y()     = <vector>     (circumference as a vector)
+#'  .x()     = <data.frame> (The other 2 columns as a data frame)
 #'  .dat()   = <data.frame> (The full data set)
 #' }
 #'
-#' If the formula `as.character(cyl) ~ .` where used:
+#' If the formula `Tree ~ .` were used:
 #' \preformatted{
-#'  .preds() =   10          (the 10 numeric columns in `mtcars`)
-#'  .cols()  =   10          (same)
-#'  .obs()   = 32
-#'  .lvls()  =  c("4" = 11, "6" = 7, "8" = 14)
+#'  .preds() =   2          (the 2 numeric columns in `Orange`)
+#'  .cols()  =   2          (same)
+#'  .obs()   = 35
+#'  .lvls()  =  c("1" = 7, "2" = 7, "3" = 7, "4" = 7, "5" = 7)
 #'  .facts() =   0
-#'  .y()     = <vector>     (as.character(cyl) as a vector)
-#'  .x()     = <data.frame> (The other 10 columns as a data frame)
+#'  .y()     = <vector>     (Tree as a vector)
+#'  .x()     = <data.frame> (The other 2 columns as a data frame)
 #'  .dat()   = <data.frame> (The full data set)
 #' }
 #'