3. Correlogram.

Library corrplot

m<-cor(iris[,-5])
corrplot.mixed(m,order="hclust", upper="pie")

Library GGally::ggpairs

library(GGally)
library(ggplot2)
data(diamonds)
d <- diamonds[sample(nrow(diamonds), 500),]
ggpairs(d[,-c(2:4)], lower=list(continuous = "smooth"))

ggpairs(
  d,
  mapping = ggplot2::aes(color = Species),
  upper = list(continuous = wrap("density", alpha = 0.5), combo = "box", discrete="facetbar"),
  lower = list(continuous = wrap("smooth_loess", alpha = 0.3), combo = wrap("dot", alpha = 0.4), discrete="facetbar"),
  diag =  list(continuous="densityDiag"),
  title = "Iris"
)