Get code working again

logicals-numbers.Rmd

@@ -4,6 +4,11 @@
 
 `between()`
 
+```{r}
+library(tidyverse)
+library(nycflights13)
+```
+
 ## Logical operators
 
 Multiple arguments to `filter()` are combined with "and": every expression must be true in order for a row to be included in the output.
@@ -57,6 +62,9 @@ You'll learn how to create new variables shortly.
     This makes `sum()` and `mean()` very useful: `sum(x)` gives the number of `TRUE`s in `x`, and `mean(x)` gives the proportion.
 
     ```{r}
+    not_cancelled <- flights %>% 
+      filter(!is.na(dep_delay), !is.na(arr_delay))
+
     # How many flights left before 5am? (these usually indicate delayed
     # flights from the previous day)
     not_cancelled %>% 
@@ -108,7 +116,7 @@ There's no way to list every possible function that you might use, but here's a
     If you need rolling aggregates (i.e. a sum computed over a rolling window), try the RcppRoll package.
 
     ```{r}
-    x
+    x <- 1:10
     cumsum(x)
     cummean(x)
     ```

missing-values.Rmd

@@ -2,6 +2,10 @@
 
 ## Introduction
 
+```{r}
+library(tidyverse)
+```
+
 ## Basics
 
 ### Missing values {#missing-values-filter}

strings.Rmd

@@ -1056,6 +1056,10 @@ So far you've learned how to tidy `table2`, `table4a`, and `table4b`, but not `t
 To fix this problem, we'll need the `separate()` function.
 You'll also learn about the complement of `separate()`: `unite()`, which you use if a single variable is spread across multiple columns.
 
+```{r}
+library(tidyr)
+```
+
 ### Separate
 
 `separate()` pulls apart one column into multiple columns, by splitting wherever a separator character appears.

vector-tools.Rmd

@@ -4,6 +4,14 @@
 
 `%in%`
 
+```{r}
+library(tidyverse)
+library(nycflights13)
+
+not_cancelled <- flights %>% 
+  filter(!is.na(dep_delay), !is.na(arr_delay))
+```
+
 ## Counts
 
 -   Counts: You've seen `n()`, which takes no arguments, and returns the size of the current group.