Line Plot in R with Error Bars

A line plot is a graphical representation of a series of data. Line plots are widely used in data visualization. In we use ggplot2( ) and plot( ) function to create line plot. Error bars act as a visual enhancement that help us to see variability of the plotted data. Error Bars are used to show standard error, standard deviation i.e. with the help of integrated error bars in our plot we can know the estimated error.

In this article we are going to create a line plot with Error Bars and without Error Bars. We can use plot() function to create scatter plot and line plot also.

Syntax:

errbar(x, y, yplus, yminus, cap=0.015, main = NULL, sub=NULL, xlab=as.character(substitute(x)), ylab=if(is.factor(x) || is.character(x)) ” “else as.character(substitute(y)), add=FALSE, lty=1, type=’p’, ylim=NULL,pch, lwd=1, errbar.col, )

Where,

Sr. no.	Parameter	Description	Default values
1.	x	It holds vector of x-axis values.	–
2.	y	It holds vector of y-axis values.	–
3.	yplus	The top value of error bars.	–
4.	yminus	The bottom value of error bars.	–
5.	cap	It is the width of cap	0.015
6.	main	The title of the plot	NULL
7.	sub	The title of sub plot	NULL
10.	add	Used to add error bars to existing plot set it to True.	False
11.	lty	The line type for error bars.	1
15.	errbar.col	To change the color of error bars	black

Approach:

• Firstly open up your rstudio
• Type the following command and hit enter to install the dependency that will help us to draw error bars in line plots.

install.packages("Hmisc")

• Load library by typing :

library(Hmisc)

• Create two data variables one for the x-axis and another for the y-axis
• Create a vector to store error values (randomly)
• Show error bars using errbar()

Example 1:

R

# Creating random data
x = c(1,2,3,4,5,6,8)
y = c(8,6,4,5,1,7,6)

# generating error_values
error_values = c(x)

# plotting
errbar(x,y,y+error_values,y-error_values,type='b')

Output : 

Fig. 1. Simple line plot with error bars.

Example 2:

R

# Creating random data
x = 10:20
y = x*2.5

# generating error_values
# you can use any custom
# function to calculate error
error_values = sqrt(y)

# plotting
errbar(x,y,y+error_values,y-error_values,type="b",
       col='black',cex=2,errbar.col='green',
       xlab="X-axis",ylab="Y-axis",
       pch="*")

Output:

Fig. 2. Custom line plot with error bars.