Update exercises before tackling #766

Author: Robinlovelace

Diff for: _04-ex.Rmd

@@ -8,16 +8,25 @@ data(nz_height, package = "spData")
 E1. It was established in Section \@ref(spatial-vec) that Canterbury was the region of New Zealand containing most of the 100 highest points in the country.
 How many of these high points does the Canterbury region contain?
 
+**Bonus:** plot the result using the `plot()` function to show all of New Zealand, `canterbury` region highlighted in yellow, high points in Canterbury represented with black dots and  
+
+
 ```{r 04-ex-e1}
 library(tmap)
 # tmap_mode("view")
 qtm(nz) + qtm(nz_height)
 canterbury = nz %>% filter(Name == "Canterbury")
 canterbury_height = nz_height[canterbury, ]
+nz_not_canterbury_height = nz_height[canterbury, , op = st_disjoint]
 nrow(canterbury_height) # answer: 70
+
+plot(nz$geom)
+plot(canterbury$geom, col = "yellow", add = TRUE)
+plot(nz_not_canterbury_height$geometry, pch = 4, col = "blue", add = TRUE)
+plot(canterbury_height$geometry, pch = 3, col = "red", add = TRUE)
 ```
 
-E2. Which region has the second highest number of `nz_height` points in, and how many does it have?
+E2. Which region has the second highest number of `nz_height` points, and how many does it have?
 
 ```{r 04-ex-e2}
 nz_height_count = aggregate(nz_height, nz, length)