Plotting Multiple Lines to One ggplot2 Graph in R (Example Code)

In this post you’ll learn how to plot two or more lines to only one ggplot2 graph in the R programming language.

Setting up the Example

data(iris)                           # Loading iris data
iris <- iris[ , 1:4]                 # Remove non-numeric data
iris$x <- 1:nrow(iris)               # Add counter
head(iris)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width x
# 1          5.1         3.5          1.4         0.2 1
# 2          4.9         3.0          1.4         0.2 2
# 3          4.7         3.2          1.3         0.2 3
# 4          4.6         3.1          1.5         0.2 4
# 5          5.0         3.6          1.4         0.2 5
# 6          5.4         3.9          1.7         0.4 6

We have to install and load the ggplot2 & reshape2 packages:

install.packages("ggplot2")          # Install ggplot2 package
library("ggplot2")                   # Load ggplot2

install.packages("reshape2")         # Install & load reshape2 package
library("reshape2")

Example: Draw Multiple Lines in One ggplot2 Graph (Iris Flower Data)

iris_long <- melt(iris, id = "x")    # Transforming data to long format
head(iris_long)                      # Printing head of long iris data
#   x     variable value
# 1 1 Sepal.Length   5.1
# 2 2 Sepal.Length   4.9
# 3 3 Sepal.Length   4.7
# 4 4 Sepal.Length   4.6
# 5 5 Sepal.Length   5.0
# 6 6 Sepal.Length   5.4
ggplot(iris_long,                    # Drawing ggplot2 plot
       aes(x = x,
           y = value,
           color = variable)) +
  geom_line()

r graph figure 1 plotting multiple lines one ggplot2 graph r

Further Resources

Have a look at the following R tutorials. They illustrate similar topics as this post:

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