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Tweak facetting section 

Fixes #1035
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Hadley Wickham 2022-09-07 17:19:24 -05:00
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data-visualize.qmd
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@ -396,9 +396,11 @@ One way to add additional variables to a plot is by mapping them to an aesthetic
Another way, which is particularly useful for categorical variables, is to split your plot into **facets**, subplots that each display one subset of the data. Another way, which is particularly useful for categorical variables, is to split your plot into **facets**, subplots that each display one subset of the data.
To facet your plot by a single variable, use `facet_wrap()`. To facet your plot by a single variable, use `facet_wrap()`.
The first argument of `facet_wrap()` is a formula, which you create with `~` followed by a variable name (here, "formula" is the bane if a data structure in R, not a synonym for "equation"). The first argument of `facet_wrap()` is a formula[^data-visualize-1], which you create with `~` followed by a variable name.
The variable that you pass to `facet_wrap()` should be discrete. The variable that you pass to `facet_wrap()` should be discrete.
[^data-visualize-1]: Here "formula" is the name of the type of thing created by `~`, not a synonym for "equation".
```{r} ```{r}
#| fig-alt: > #| fig-alt: >
#| Scatterplot of highway fuel efficiency versus engine size of cars, #| Scatterplot of highway fuel efficiency versus engine size of cars,
@ -409,9 +411,8 @@ ggplot(data = mpg) +
facet_wrap(~cyl) facet_wrap(~cyl)
``` ```
To facet your plot on the combination of two variables, add `facet_grid()` to your plot call. To facet your plot with the combination of two variables, switch from `facet_wrap()` to `facet_grid()`.
The first argument of `facet_grid()` is also a formula. The first argument of `facet_grid()` is also a formula, but now it's a double sided formula: `rows ~ cols`.
This time the formula should contain two variable names separated by a `~`.
```{r} ```{r}
#| fig-alt: > #| fig-alt: >
@ -426,8 +427,6 @@ ggplot(data = mpg) +
facet_grid(drv ~ cyl) facet_grid(drv ~ cyl)
``` ```
If you prefer to not facet in the rows or columns dimension, use a `.` instead of a variable name, e.g. `+ facet_grid(. ~ cyl)`.
### Exercises ### Exercises
1. What happens if you facet on a continuous variable? 1. What happens if you facet on a continuous variable?