How to create a horizontal line in ggplot2 graph with different color in R?

To create a horizontal line in ggplot2 graph with different in R, we can follow the below steps −

• First of all, create a data frame.
• Then, create a plot using ggplot2 using geom_hline function having horizontal line.
• After that, create the same plot with line color defined with col argument.

Create the data frame

Let's create a data frame as shown below −

 Live Demo

x<-sample(1:100,20)
y<-sample(1:1000,20)
df<-data.frame(x,y)
df

On executing, the above script generates the below output(this output will vary on your system due to randomization) −

    x  y
1  85  35
2  91  593
3  19  491
4  40  601
5  84  283
6  18  179
7  88  349
8  47  769
9  30  279
10 62  881
11 3   930
12 94  429
13 77  576
14 52  792
15 37  757
16 89  405
17 73  713
18 23 72
19 96 931
20 92 350

Create the plot with ggplot2

Using ggplot2 function to create the scatterplot between x and y with horizontal line at 600 −

x<-sample(1:100,20)
y<-sample(1:1000,20)
df<-data.frame(x,y)
library(ggplot2)
ggplot(df,aes(x,y))+geom_point()+geom_hline(yintercept=600)

Output

Create the plot with colored horizontal line

Using col argument inside geom_hline to create the colored horizontal line −

x<-sample(1:100,20)
y<-sample(1:1000,20)
df<-data.frame(x,y)
library(ggplot2)
ggplot(df,aes(x,y))+geom_point()+geom_hline(yintercept=600,col=2)

Output