R: Data Analysis and Visualization

Highlighting grouped data points by size and symbol type

Sometimes, we might not want to use different colors to represent different groups of data points. For example, some journals accept graphs only in grayscale. In this recipe, we will learn how we can highlight grouped data points by symbol size and type.

Getting ready

We will use the ggplot2 library, so let's load it by running the following command:

library(ggplot2)

How to do it...

First, let's group points by the symbol type. Once again, we use the qplot() function:

qplot(disp,mpg,data=mtcars,shape=as.factor(cyl)) 

Next, let's group the points simply by the size of the plotting symbol:

qplot(disp,mpg,data=mtcars,size=as.factor(cyl)) ...