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How to Draw a Legend Outside of a Plot in R?

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  • Last Updated : 19 Dec, 2021

In this article, we will discuss how to draw a legend outside of a Plot in the R Programming Language.

We first create a basic plot without legend using the plot() function and add a margin around it for legend by using the par() function of the R Language. We will create the required margin and make the xpd parameter TRUE. This will make our plotting clipped to the figure region.

Syntax:

par( mar, xpd)

where,

  • mar: determines the vector which contains margin.
  • xpd: It is a boolean. If FALSE, all plotting is clipped to the plot region, if TRUE, all plotting is clipped to the figure region

Then we use the legend() function to add a legend layer on top of it. To put the legend at the desired position on the plot we use the inset parameter of the legend function.

Syntax:

legend(position, inset, title, legend, pch, col )

where,

  • position: determines the position of the legend.
  • inset: determines the shift in position.
  • title: determines the title of legend.
  • pch: determines the symbols used to represent the data point.
  • col: determines the color of data points.

Example 1:

Here, is a basic plot in the R Language with the legend on the top right corner of the plot.

R




# create sample data frame
sample_data <- data.frame(x = c(rnorm(50), rnorm(50, 5)),      
                   y = c(rnorm(50), rnorm(50, 5)),
                   group = c(rep(1, 50), rep(2, 50))) 
  
# create margin around plot
par(mar = c(3, 3, 3, 8), xpd = TRUE)
  
# Draw scatter plot
plot(sample_data$x, sample_data$y,                                   
     pch = sample_data$group+10,
     col = sample_data$group)
  
# Draw legend
legend("topright", inset = c(-0.3, 0.1),                   
       legend = c("Group 1","Group 2"),
       pch = c(11,12), col = 1:2)

Output:

Example 2:

Here, is a basic plot in the R Language with the legend on the bottom of the plot.

R




# create sample data frame
sample_data <- data.frame(x = c(rnorm(50), rnorm(50, 5), rnorm(50, 10)),      
                   y = c(rnorm(50), rnorm(50, 5), rnorm(50, 10)),
                   group = c(rep(1, 50), rep(2, 50), rep(3, 50))) 
  
# create margin around plot
par(mar = c(10, 3, 3, 3), xpd = TRUE)
  
# Draw scatter plot
plot(sample_data$x, sample_data$y,                                   
     pch = sample_data$group+10,
     col = sample_data$group)
  
# Draw legend
legend("topright", inset = c(0.4, 1.2),                   
       legend = c("Group 1","Group 2","Group 3"),
       pch = c(11,12,13), col = 1:3)

Output:


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