This tutorial explains how to plot multiple lines (i.e. data series) in one chart in R.

To plot multiple lines in one chart, we can either use base R or install a fancier package like ggplot2.

**Using Base R**

Here are two examples of how to plot multiple lines in one chart using Base R.

**Example 1: Using Matplot**

If you have a dataset that is in a wide format, one simple way to plot multiple lines in one chart is by using matplot:

#Create a fake dataset with 3 columns (ncol=3) composed of randomly generated #numbers from a uniform distribution with minimum = 1 and maximum = 10 data <- matrix(runif(30,1,10), ncol=3) data [,1] [,2] [,3] #[1,] 5.371653 3.490919 3.953603 #[2,] 9.551883 2.681054 9.506765 #[3,] 3.525686 1.027758 8.059011 #[4,] 9.923080 1.337935 1.112361 #[5,] 7.273972 7.627546 1.174340 #[6,] 8.859109 3.778144 9.384526 #[7,] 9.614542 3.866029 7.301729 #[8,] 9.288085 5.804041 8.347907 #[9,] 1.696849 4.650687 7.220209 #[10,] 5.820941 4.799682 5.243663 #plot the three columns of the dataset as three lines and add a legend in #the top right corner of the chart matplot(data, type = "b",pch=1,col = 1:3) legend("topright", legend = 1:3, col=1:3, pch=1)

This code generates the following chart:

**Example 2: Using Points & Lines**

Another way to plot multiple lines is to plot them one by one, using the built-in R functions points() and lines(). The code below demonstrates an example of this approach:

#generate an x-axis along with three data series x <- c(1,2,3,4,5,6) y1 <- c(2,4,7,9,12,19) y2 <- c(1,5,9,8,9,13) y3 <- c(3,6,12,14,17,15)#plot the first data series using plot() plot(x, y1, type="o", col="blue", pch="o", ylab="y", lty=1) #add second data series to the same chart using points() and lines() points(x, y2, col="red", pch="*") lines(x, y2, col="red",lty=2) #add third data series to the same chart using points() and lines() points(x, y3, col="dark red",pch="+") lines(x, y3, col="dark red", lty=3) #add a legend in top left corner of chart at (x, y) coordinates = (1, 19) legend(1,19,legend=c("y1","y2","y3"), col=c("blue","red","black"), pch=c("o","*","+"),lty=c(1,2,3), ncol=1)

This code generates the following chart:

**Using ggplot2**

Here is an example of how to plot multiple lines in one chart using ggplot2.

#install (if not already installed) and load ggplot2 package if(!require(ggplot2)){install.packages('ggplot2')} #generate fake dataset with three columns 'x', 'value', and 'variable' data <- data.frame(x=rep(1:5, 3), value=sample(1:100, 15), variable=rep(paste0("series", 1:3), each=5)) data # x value variable #1 1 93 series1 #2 2 64 series1 #3 3 36 series1 #4 4 17 series1 #5 5 95 series1 #6 1 80 series2 #7 2 33 series2 #8 3 69 series2 #9 4 70 series2 #10 5 65 series2 #11 1 11 series3 #12 2 10 series3 #13 3 94 series3 #14 4 40 series3 #15 5 88 series3 #plot all three series on the same chart using geom_line() ggplot(data = data, aes(x=x, y=value)) + geom_line(aes(colour=variable))

This generates the following chart: