6.7 Three or more continuous variables: Scatterplot matrix

To show all pairwise relationships between more than two continuous variables, use a scatterplot matrix.

6.7.1 Base R

Use pairs() to plot all pairwise combinations of columns of a data.frame. As we only want to plot pairs of continuous variables here, we first select just those variables.

pairs(subset(mydat,
             select = c("stheight", "stweight", "bmi", "bmipct")),
      labels = c("Height", "Weight", "BMI", "BMI-pctle"))

6.7.2 ggplot

In ggplot(), use the GGally library (Schloerke et al. 2024) to get the ggpairs() function which gives you not only scatterplots, but also a density curve for each variable and all pairwise correlations. See ?ggpairs for details.

library(GGally)

mydat %>% 
  select(stheight, stweight, bmi, bmipct) %>% 
  ggpairs(columnLabels = c("Height", "Weight", "BMI", "BMI-pctle"))

References

Schloerke, Barret, Di Cook, Joseph Larmarange, Francois Briatte, Moritz Marbach, Edwin Thoen, Amos Elberg, and Jason Crowley. 2024. GGally: Extension to Ggplot2. https://ggobi.github.io/ggally/.