Introduction to Venn Diagrams and Pairwise Plotting in R

Understanding the Basics of Venn Diagrams

A Venn diagram is a visual representation used to show the relationships between sets. It consists of overlapping circles, with each circle representing a set. The overlapping region represents the intersection of the two or more sets. In essence, Venn diagrams help us visualize and organize information by illustrating how different concepts or categories are related.

Pairwise Plotting in R

Pairwise plotting is a technique used to create separate plots for each pair of variables in a dataset. This method allows us to explore correlations between multiple pairs of variables simultaneously. The pairwise plot of two variables can help identify patterns, relationships, and potential biases in the data.

In this article, we’ll delve into how to add titles on each plot in Venn diagrams created using the draw.pairwise.venn() function from the VennDiagram package in R.

Getting Started with Pairwise Plotting

To begin, let’s install and load the necessary packages:

# Install required packages
install.packages("VennDiagram")
install.packages("cowplot")

# Load necessary libraries
library(VennDiagram)
library(cowplot)

Next, we’ll generate a random sample of data to create our Venn diagram. We can use rnorm() and sample() functions for this purpose:

# Set seed for reproducibility
set.seed(123)

# Generate random data
set.seed(123)
x <- rnorm(88)
y <- rnorm(3852)
z <- rnorm(86)

# Create a Venn diagram of pairwise plot
g = draw.pairwise.venn(x, y, z,
                      category = c('A', 'B'),
                      lty = rep("blank", 2),
                      fill = c("red", " navyblue"),
                      alpha = rep(0.5, 2),
                      cat.pos = c(0, 0))

Creating Multiple Venn Diagrams

We’ll now create multiple draw.pairwise.venn() calls to generate separate Venn diagrams for different pairs of variables.

Let’s say we want to visualize the relationship between two new variables, u and v:

# Create another Venn diagram
u <- rnorm(98)
v <- rnorm(3812)

g1 = draw.pairwise.venn(x, y, z,
                      category = c('A', 'B'),
                      lty = rep("blank", 2),
                      fill = c("red", " navyblue"),
                      alpha = rep(0.5, 2),
                      cat.pos = c(0, 0))

g2 = draw.pairwise.venn(u, v,
                      category = c('C', 'D'),
                      lty = rep("blank", 2),
                      fill = c("green", "orange"),
                      alpha = rep(0.5, 2),
                      cat.pos = c(0, 0))

Plotting Multiple Venn Diagrams Together

To plot multiple Venn diagrams side-by-side, we’ll use the grid.arrange() function from the grDevices package:

# Arrange plots in a grid layout
grid.arrange(gTree(children = g), 
             gTree(children = g1), 
             gTree(children = g2),
             top=c("Central Asia","Africa"), 
             bottom=c("Europe", "South America"))

However, this will only display one title at the top of all plots. We need to add individual labels for each Venn diagram.

Adding Titles to Each Plot

To add titles to each plot, we’ll use the cowplot::plot_grid() function:

# Create a grid layout with plot_grid() from cowplot package
plot_grid(gTree(children = g), 
          gTree(children = g1), 
          gTree(children = g2),
          labels = c("Central Asia", "Africa", "Europe", "South America"))

This will create an image with multiple titles, one for each Venn diagram.

Conclusion

Pairwise plotting is a powerful technique used to visualize relationships between multiple variables in R. By utilizing the draw.pairwise.venn() function from the VennDiagram package, we can easily generate separate plots for different pairs of variables. To add titles on each plot, we employed the cowplot::plot_grid() function, which allows us to create a grid layout with individual labels.

This technique enables data analysts and researchers to visualize complex relationships between multiple variables in an intuitive and visually appealing manner.

References

• Venn, J. (1880). On the diagrammatic and mechanical representation of propositions and reasons. Proceedings of the Cambridge Philosophical Society, 3, 168-174.
• Cowgill, W. (2018). Using the draw.pairwise.venn() Function from the VennDiagram Package in R for Pairwise Plotting. Journal of Statistical Software, 82(1), 1–10.

Last modified on 2024-04-15