Chapter 8 Default Scatter Plot Matrices in R

Scatter Plot Matrices:

par(mfrow=c(2,1))
pairs(~mpg+disp+drat+wt,data=mtcars, 
   main="Simple Scatterplot Matrix")

pairs(~mpg+disp+drat+wt,data=mtcars,lower.panel = NULL,
   main="Simple Scatterplot Matrix")

Color points by groups Scatter plots:

my_col <- c("#00AFBB", "#E7B800", "#FC4E07")  
pairs(iris[,1:4], pch = 19,  cex = 0.5,
      col = my_col[iris$Species],
      lower.panel=NULL)

Add correlations on the lower panels:

# Correlation panel
my_col <- c("#00AFBB", "#E7B800", "#FC4E07") 
panel.cor <- function(x, y){
    usr <- par("usr"); on.exit(par(usr))
    par(usr = c(0, 1, 0, 1))
    r <- round(cor(x, y), digits=2)
    txt <- paste0("R = ", r)
    cex.cor <- 0.8/strwidth(txt)
    text(0.5, 0.5, txt, cex = cex.cor * r)
}
# Customize upper panel
upper.panel<-function(x, y){
  points(x,y, pch = 19, col = my_col[iris$Species])
}
# Create the plots
pairs(iris[,1:4], 
      lower.panel = panel.cor,
      upper.panel = upper.panel)

Add correlations on the scatter plots:

my_col <- c("#00AFBB", "#E7B800", "#FC4E07")
# Customize upper panel
upper.panel<-function(x, y){
  points(x,y, pch=19, col=c("red", "green3", "blue")[iris$Species])
  r <- round(cor(x, y), digits=2)
  txt <- paste0("R = ", r)
  usr <- par("usr"); on.exit(par(usr))
  par(usr = c(0, 1, 0, 1))
  text(0.5, 0.9, txt)
}
pairs(iris[,1:4], lower.panel = NULL, 
      upper.panel = upper.panel)

Additional-> the R package psych:

#install.packages("psych")
library(psych)

## 
## Attaching package: 'psych'

## The following object is masked from 'package:car':
## 
##     logit

pairs.panels(iris[,-5], 
             method = "pearson", # correlation method
             hist.col = "#52E932",
             density = TRUE,  # show density plots
             ellipses = TRUE # show correlation ellipses
             )