# Correlation matrix with ggally

This post explains how to build a correlogram with the `ggally` R package. It provides several reproducible examples with explanation and `R` code.

# Scatterplot matrix with `ggpairs()`

The `ggpairs()` function of the `GGally` package allows to build a great scatterplot matrix.

Scatterplots of each pair of numeric variable are drawn on the left part of the figure. Pearson correlation is displayed on the right. Variable distribution is available on the diagonal.

# Visualize correlation with `ggcorr()`

The `ggcorr()` function allows to visualize the correlation of each pair of variable as a square. Note that the `method` argument allows to pick the correlation type you desire.

# Split by group

It is possible to use ggplot2 aesthetics on the chart, for instance to color each category.

``````# Quick display of two cabapilities of GGally, to assess the distribution and correlation of variables
library(GGally)

# From the help page:
data(flea)
ggpairs(flea, columns = 2:4, ggplot2::aes(colour=species)) ``````

# Change plot types

Change the type of plot used on each part of the correlogram. This is done with the `upper` and `lower` argument.

``````# Quick display of two cabapilities of GGally, to assess the distribution and correlation of variables
library(GGally)

# From the help page:
data(tips, package = "reshape")
ggpairs(
tips[, c(1, 3, 4, 2)],
upper = list(continuous = "density", combo = "box_no_facet"),
lower = list(continuous = "points", combo = "dot_no_facet")
)``````

Related chart types

Scatter
Heatmap
Correlogram
Bubble
Connected scatter
Density 2d

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