Plotting Multiple Graphs in R

 

Plotting Multiple Graphs in R

By default, R displays one graph at a time. When a new plot command is executed, the previous graph is replaced. R provides several methods to display multiple graphs:

  1. Using par() with mfrow
  2. Using par() with mfcol
  3. Opening multiple graphics windows using windows()
  4. Saving multiple plots to a PDF file
  5. Using separate PNG/JPEG files
  6. Using layout()
  7. Using split.screen()

1. Using par() Function

The par() function sets graphical parameters.

Syntax

par(mfrow=c(rows, columns))

where

  • rows = number of rows
  • columns = number of columns

Example 1: Four Plots in a 2×2 Layout

par(mfrow=c(2,2))
load(iris)
hist(iris$Sepal.Length,
     col="skyblue",
     main="Histogram")

boxplot(iris$Sepal.Length,
        col="green",
        main="Box Plot")

plot(iris$Sepal.Length,
     iris$Petal.Length,
     col="red",
     pch=19,
     main="Scatter Plot")

barplot(table(iris$Species),
        col=rainbow(3),
        main="Bar Plot")

Layout:

+-----------+-----------+
| Histogram | Box Plot  |
+-----------+-----------+
| Scatter   | Bar Plot  |
+-----------+-----------+



Restoring Default Setting

par(mfrow=c(1,1))

This restores the default single-graph display.

Example 2: Two Plots Side by Side

par(mfrow=c(1,2))

hist(iris$Sepal.Length)
boxplot(iris$Sepal.Length)

par(mfrow=c(1,1))

Layout:

+------------+------------+
| Histogram  | Box Plot   |
+------------+------------+



Example 3: Two Plots Vertically

par(mfrow=c(2,1))

hist(iris$Sepal.Length)

boxplot(iris$Sepal.Length)

par(mfrow=c(1,1))

Layout:

+------------+
| Histogram  |
+------------+
| Box Plot   |
+------------+



2. Using mfcol

Plots are filled column-wise instead of row-wise.

Example

par(mfcol=c(2,2))

hist(iris$Sepal.Length)
boxplot(iris$Sepal.Length)
plot(iris$Sepal.Length,iris$Petal.Length)
barplot(table(iris$Species))

Arrangement:

1 3
2 4

whereas mfrow gives

1 2
3 4



3. Using windows()

windows() opens a new graphics window.

Windows only

windows()

hist(iris$Sepal.Length)

Open another window:

windows()

boxplot(iris$Sepal.Length)

Open third window:

windows()

plot(iris$Sepal.Length,
     iris$Petal.Length)

Each graph appears in a separate window.

Linux

Use

x11()

instead of windows().

Example:

x11()

hist(iris$Sepal.Length)

Mac OS

Use

quartz()

Example:

quartz()

boxplot(iris$Sepal.Length)

4. Saving Multiple Graphs to a PDF

pdf("graphs.pdf")

hist(iris$Sepal.Length)

boxplot(iris$Sepal.Length)

plot(iris$Sepal.Length,
     iris$Petal.Length)

barplot(table(iris$Species))

dev.off()

The file graphs.pdf contains four pages, each with one graph.

5. Saving Individual Graphs as PNG

png("histogram.png")

hist(iris$Sepal.Length)

dev.off()

Another graph:

png("boxplot.png")

boxplot(iris$Sepal.Length)

dev.off()

6. Using layout()

layout() gives more control than par().

Example

layout(matrix(c(1,2,3,4),2,2))

hist(iris$Sepal.Length)

boxplot(iris$Sepal.Length)

plot(iris$Sepal.Length,
     iris$Petal.Length)

barplot(table(iris$Species))

Layout:

1 3
2 4

Unequal Layout

layout(matrix(c(1,2,3,3),2,2,byrow=TRUE))

Layout:

1 2
3 3

Plot 3 occupies the entire bottom row.

Example:

layout(matrix(c(1,2,3,3),2,2,byrow=TRUE))

hist(iris$Sepal.Length)

boxplot(iris$Sepal.Length)

plot(iris$Sepal.Length,
     iris$Petal.Length)


7. Using split.screen()

split.screen(c(1,2))

Creates four screens.

Screen 1

screen(1)

hist(iris$Sepal.Length)

Screen 2

screen(2)

boxplot(iris$Sepal.Length)



Checking Active Graphics Devices

Current device:

dev.cur()

Example output:

RStudioGD
2

List active devices:

dev.list()

Example:

pdf
2

windows
3

Closing Graphics Device

Close current device:

dev.off()

Close all devices:

graphics.off()

Summary of Methods

MethodPurpose
par(mfrow=c(r,c))    Multiple plots row-wise
par(mfcol=c(r,c))    Multiple plots column-wise
windows()    New graphics window (Windows)
x11()    New graphics window (Linux)
quartz()    New graphics window (Mac)
layout()    Custom plot arrangement
split.screen()    Divide screen into sections
pdf()    Save multiple plots to PDF
png()    Save graph as image
dev.off()    Close current graphics device
graphics.off()    Close all graphics devices

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