Adding Straight Lines to a Plot in R Programming - abline() Function Last Updated : 15 Jul, 2025 Comments Improve Suggest changes Like Article Like Report abline() function in R Language is used to add one or more straight lines to a graph. The abline() function can be used to add vertical, horizontal or regression lines to plot. Syntax: abline(a=NULL, b=NULL, h=NULL, v=NULL, ...) Parameters: a, b: It specifies the intercept and the slope of the line h: specifies y-value for horizontal line(s) v: specifies x-value(s) for vertical line(s) Returns: a straight line in the plot Example 1: To add a vertical line to the plot r # add line to square plot # first example : Add one line plot(cars) abline(v = 16, col = "darkgreen") # second example : add 2 lines # addline to square plot # change line colors, sizes and types plot(cars) abline(v = c(16, 22), col = c("darkgreen", "blue"), lty = c(1, 2), lwd = c(1, 3)) # third example set.seed(1200); mydata<-rnorm(180) hist(mydata, col="darkgreen") # lwd=line width, lty =linetype abline(v = mean(mydata), col = "blue", lwd = 4, lty = 4) Output: Here, in above example straight line is added using abline() to different graphical plots Example 2: To add a horizontal line r # R program to add a horizontal line # to a plot # Creating a plot plot(cars) # Calling abline() function abline(h = 60, col = "darkgreen") Output: In above example abline() Function draws an horizontal line on the current plot at the specified ‘x’ coordinates. Example 3: To add a regression line r par(mgp = c(2, 1, 0), mar = c(3, 3, 1, 1)) # Fit regression line require(stats) reg<-lm(dist ~ speed, data = cars) coeff = coefficients(reg) # equation of the line : eq = paste0("y = ", round(coeff[1], 1), "*x ", round(coeff[2], 1)) # plot plot(cars, main = eq) abline(reg, col = "darkgreen") Output: In the above example, straight-line is added using the line equation and abline() function and plot relation between speed and distance. Comment More info K kaurbal1698 Follow Improve Article Tags : R Language R Plot-Function Explore R Tutorial | Learn R Programming Language 4 min read IntroductionR Programming Language - Introduction 4 min read Interesting Facts about R Programming Language 4 min read R vs Python 5 min read Environments in R Programming 3 min read Introduction to R Studio 4 min read How to Install R and R Studio? 4 min read Creation and Execution of R File in R Studio 5 min read Clear the Console and the Environment in R Studio 2 min read Hello World in R Programming 2 min read Fundamentals of RBasic Syntax in R Programming 3 min read Comments in R 3 min read R-Operators 5 min read R-Keywords 2 min read R-Data Types 5 min read VariablesR Variables - Creating, Naming and Using Variables in R 5 min read Scope of Variable in R 5 min read Dynamic Scoping in R Programming 5 min read Lexical Scoping in R Programming 4 min read Input/OutputTaking Input from User in R Programming 7 min read Printing Output of an R Program 4 min read Print the Argument to the Screen in R Programming - print() Function 2 min read Control FlowControl Statements in R Programming 4 min read Decision Making in R Programming - if, if-else, if-else-if ladder, nested if-else, and switch 3 min read Switch case in R 2 min read For loop in R 5 min read R - while loop 5 min read R - Repeat loop 2 min read goto statement in R Programming 2 min read Break and Next statements in R 3 min read FunctionsFunctions in R Programming 5 min read Function Arguments in R Programming 4 min read Types of Functions in R Programming 6 min read Recursive Functions in R Programming 4 min read Conversion Functions in R Programming 4 min read Data StructuresData Structures in R Programming 4 min read R Strings 6 min read R-Vectors 4 min read R-Lists 6 min read R - Array 7 min read R-Matrices 10 min read R-Factors 4 min read R-Data Frames 6 min read Object Oriented ProgrammingR-Object Oriented Programming 7 min read Classes in R Programming 3 min read R-Objects 3 min read Encapsulation in R Programming 3 min read Polymorphism in R Programming 6 min read R - Inheritance 7 min read Abstraction in R Programming 3 min read Looping over Objects in R Programming 5 min read S3 class in R Programming 8 min read Explicit Coercion in R Programming 3 min read Error HandlingHandling Errors in R Programming 3 min read Condition Handling in R Programming 5 min read Debugging in R Programming 3 min read Like