Update extending-ggplot2.Rmd (#3114)

Chester Ismay · yutannihilation · commit 140f27b74c41 · 2019-02-03T09:16:26.000+09:00
diff --git a/vignettes/extending-ggplot2.Rmd b/vignettes/extending-ggplot2.Rmd
@@ -61,7 +61,7 @@ StatChull <- ggproto("StatChull", Stat,
 )
 ```
 
-The two most important components are the `compute_group()` method (which does the computation), and the `required_aes` field, which lists which aesthetics must be present in order to for the stat to work.
+The two most important components are the `compute_group()` method (which does the computation), and the `required_aes` field, which lists which aesthetics must be present in order for the stat to work.
 
 Next we write a layer function. Unfortunately, due to an early design mistake I called these either `stat_()` or `geom_()`. A better decision would have been to call them `layer_()` functions: that's a more accurate description because every layer involves a stat _and_ a geom. 
 

Original file line number	Diff line number	Diff line change
`@@ -61,7 +61,7 @@ StatChull <- ggproto("StatChull", Stat,`
`61`	`61`	`)`
`62`	`62`	```
`63`	`63`
`64`		-The two most important components are the `compute_group()` method (which does the computation), and the `required_aes` field, which lists which aesthetics must be present in order to for the stat to work.
	`64`	+The two most important components are the `compute_group()` method (which does the computation), and the `required_aes` field, which lists which aesthetics must be present in order for the stat to work.
`65`	`65`
`66`	`66`	Next we write a layer function. Unfortunately, due to an early design mistake I called these either `stat_()` or `geom_()`. A better decision would have been to call them `layer_()` functions: that's a more accurate description because every layer involves a stat _and_ a geom.
`67`	`67`