More comments from @csgillespie

functions.Rmd

@@ -154,12 +154,6 @@ This is an important part of the "do not repeat yourself" (or DRY) principle. Th
     write your own functions to compute the variance and skew of a numeric 
     vector.
 
-1.  Implement a `fizzbuzz` function. It takes a single number as input. If
-    the number is divisible by three, it returns "fizz". If it's divisible by
-    five it returns "buzz". If it's divisible by three and five, it returns
-    "fizzbuzz". Otherwise, it returns the number. Make sure you first write 
-    working code before you create the function.
-    
 1.  Write `both_na()`, a function that takes two vectors of the same length 
     and returns the number of positions that have an `NA` in both vectors.
 
@@ -284,7 +278,7 @@ if (condition) {
 }
 ```
 
-To get help on `if` you need to surround it in backticks: `` ?`if` ``.
+To get help on `if` you need to surround it in backticks: `` ?`if` ``. The help isn't particularly helpful if you're not already an experienced programmer, but at least you know how to get to it!
 
 Here's a simple function that uses an if statement. The goal of this function is to return a logical vector describing whether or not each element of a vector is named.
 
@@ -419,6 +413,12 @@ if (y < 20) {
     argument that defaults to `lubridate::now()`. That will make it 
     easier to test your function.)
 
+1.  Implement a `fizzbuzz` function. It takes a single number as input. If
+    the number is divisible by three, it returns "fizz". If it's divisible by
+    five it returns "buzz". If it's divisible by three and five, it returns
+    "fizzbuzz". Otherwise, it returns the number. Make sure you first write 
+    working code before you create the function.
+    
 1.  How could you use `cut()` to simplify this set of nested if-else statements?
 
     ```{r, eval = FALSE}

vectors.Rmd

@@ -149,7 +149,8 @@ Normally you don't need to know about these different types because you can alwa
 
 1.  Describe the difference between `is.finite(x)` and  `!is.infinite(x)`.
 
-1.  Read the source code for `dplyr::near()`. How does it work?
+1.  Read the source code for `dplyr::near()` (Hint: to see the source code,
+    drop the `()`). How does it work? 
 
 1.  A logical vector can take 3 possible values. How many possible
     values can an integer vector take? How many possible values can
@@ -211,7 +212,7 @@ if (length(x)) {
 }
 ```
 
-In this case, 0 is converted to `FALSE` and everything else is converted to `TRUE`. I think this makes it harder to understand your code, and I don't recommend it.
+In this case, 0 is converted to `FALSE` and everything else is converted to `TRUE`. I think this makes it harder to understand your code, and I don't recommend it. Instead be explicit: `length(x) > 0`.
 
 It's also important to understand what happens when you try and create a vector containing multiple types with `c()`: the most complex type always wins.