Update iteration.qmd (#1071)

Provided another way of getting R squared by using `nest()` from tidyr, which makes the code to be tidyverse consistent.

iteration.qmd

@@ -612,6 +612,18 @@ models |>
   map_dbl("r.squared")
 ```
 
+Another way to obtain R squared is by using the broom package. Instead of using `split()` from base R, you can use `nest()` from tidyr:
+
+```{r}
+mtcars |>
+  nest(data = -cyl) |>
+  arrange(cyl) |>
+  mutate(mod = map(data, ~lm(mpg ~ wt, data = .)),
+         glanced = map(mod, broom::glance)) |>
+  unnest(glanced) %>%
+  pull(r.squared)
+```
+
 You can also use an integer to select elements by position:
 
 ```{r}
@@ -705,7 +717,7 @@ str(safe_log("a"))
 When the function succeeds, the `result` element contains the result and the `error` element is `NULL`.
 When the function fails, the `result` element is `NULL` and the `error` element contains an error object.
 
-`safely()` is designed to work with map:
+`safely()` is designed to work with `map()`:
 
 ```{r}
 x <- list(1, 10, "a")