#### Overview of this book

R Graph Essentials
Credits
www.PacktPub.com
Preface
Free Chapter
Base Graphics in R – One Step at a Time
Creating Graphs with ggplot
Index

## Creating facet plots

If you have a large dataset that includes a categorical variable, you can use the `facets` command to produce multiple graphs: one for each level of the categorical variable. In the following example, we will create a graph for each level of `ETH` (1, 2, and 3) using `facets = ETH ~ .` Note the tilde sign followed by the period. Enter this syntax:

```qplot(HEIGHT, WEIGHT_1, data = T,  geom = "point",  main = "HEIGHT VS. WEIGHT BY ETHNICITY", xlab = "WEIGHT BEFORE TREATMENT (Kg)", ylab = "HEIGHT (cm)", facets = ETH ~ .)
```

Our facet plot is as follows:

Indeed, we have three scatterplots arranged vertically: one for each level of `ETHNICITY`. We can also create facet plots across the levels of two factor variables. In the following code, we will create a scatterplot of `HEIGHT` against `WEIGHT_1` for each combination of SMOKE and EXERCISE in each facet, where the two levels of gender are represented by shape and color. Here is the required command:

`qplot(HEIGHT, WEIGHT_1, data=T, shape=factor...`