## 5.2 Grouping Points Together using Shapes or Colors

### 5.2.1 Problem

You want to visually group points by some variable (the grouping variable), using different shapes or colors.

### 5.2.2 Solution

Map the grouping variable to the aesthetic of `shape` or `colour`. We’ll use three columns from the `heightweight` data set for this example:

``````library(gcookbook) # Load gcookbook for the heightweight data set

# Show the head of the three columns we'll use
heightweight %>%
select(sex, ageYear, heightIn)
#>     sex ageYear heightIn
#> 1     f   11.92     56.3
#> 2     f   12.92     62.3
#> 3     f   12.75     63.3
#>  ...<230 more rows>...
#> 235   m   13.67     61.5
#> 236   m   13.92     62.0
#> 237   m   12.58     59.3``````

We can use the aesthetics of `colour` or `shape` to visually differentiate the data points belonging to different categories of `sex`. We do this by mapping `sex` to one of the aesthetics `colour` or `shape` (Figure5.3):

### 5.2.3 Discussion

The grouping variable you choose must be categorical – in other words, a factor or character vector. If the grouping variable is a numeric vector, you should convert it to a factor first.

It is possible to map a variable to both `shape` and `colour`, or, if you have multiple grouping variables, to map each grouping variable to a different aesthetic. Here, we’ll map the variable `sex` to both `shape` and `colour` aesthetics (Figure 5.4, left):

``````ggplot(heightweight, aes(x = ageYear, y = heightIn, shape = sex, colour = sex)) +
geom_point()``````

You may want to use different shapes and colors than are given by the default settings. You can select other shapes for the grouping variables using `scale_shape_manual()`, and select other colors using `scale_colour_brewer()` or `scale_colour_manual()`. (Figure 5.4, right):

``````ggplot(heightweight, aes(x = ageYear, y = heightIn, shape = sex, colour = sex)) +
geom_point() +
scale_shape_manual(values = c(1,2)) +
scale_colour_brewer(palette = "Set1")``````

### 5.2.4 See Also

To use different shapes, see Recipe 5.3.

For more on using different colors, see Chapter 12.