Minor fixes

Fixes #1324

iteration.qmd

@@ -118,7 +118,7 @@ In simple cases, as above, this will be a single existing function.
 This is a pretty special feature of R: we're passing one function (`median`, `mean`, `str_flatten`, ...) to another function (`across`).
 This is one of the features that makes R a functional programming language.
 
-It's important to note that we're passing this function to `across()`, so `across()` can call it, not calling it ourselves.
+It's important to note that we're passing this function to `across()`, so `across()` can call it; we're calling it ourselves.
 That means the function name should never be followed by `()`.
 If you forget, you'll get an error:
 

layers.qmd

@@ -383,8 +383,6 @@ ggplot(mpg, aes(x = displ, y = hwy)) +
   )
 ```
 
-(You'll learn how `filter()` works in the chapter on data transformations: for now, just know that this command selects only the subcompact cars.)
-
 Geoms are the fundamental building blocks of ggplot2.
 You can completely transform the look of your plot by changing its geom, and different geoms can reveal different features of your data.
 For example, the histogram and density plot below reveal that the distribution of highway mileage is bimodal and right skewed while the boxplot reveals two potential outliers.

numbers.qmd

@@ -639,7 +639,7 @@ We won't explain `sd()` here since you're probably already familiar with it, but
 
 We can use this to reveal a small oddity in the `flights` data.
 You might expect the spread of the distance between origin and destination to be zero, since airports are always in the same place.
-But the code below makes it looks like one airport, [EGE](https://en.wikipedia.org/wiki/Eagle_County_Regional_Airport), might have moved.
+But the code below reveals a data oddity for airport [EGE](https://en.wikipedia.org/wiki/Eagle_County_Regional_Airport):
 
 ```{r}
 flights |> 
@@ -773,6 +773,7 @@ For example:
 
 3.  Create a plot to further explore the adventures of EGE.
     Can you find any evidence that the airport moved locations?
+    Can you find another variable that might explain the difference?
 
 ## Summary