Dealing with over-plotting, alpha blending

Another popular technique is known as alpha blending. It consists on making points translucent, this way the audience gets to know if points are stacked or not.  Between all the techniques demonstrated so far, alpha blending must be the most popular one. This recipe teaches how to apply alpha blending using ggplot2, plotly, and ggvis.

How to do it...

1. Set the alpha parameter to apply alpha blending to ggplot:

> library(ggplot2)
> sca1 <- ggplot( iris, aes( x = Petal.Length, y = Petal.Width))
> sca1 + geom_point( alpha = .5 , 
                     aes(shape = Species, colour = Species))

The following figure 2.7 shows alpha blending working:

Figure 2.7 - alpha blending with ggplot2.

2. Setting alpha parameter with plotly will also apply alpha blending:

> library(plotly)
> sca9 <- plot_ly( iris, x = ~Petal.Length, y = ~Petal.Width, 
>                  type = 'scatter', mode = 'markers', alpha = .5, symbol = ~Species)
> sca9

3. ggvis applies...