Plot a vertical or horizontal straight line in MatLab

What is a line?

In Geometry, a line is a connection between two continuous points. So, a line is a connective path of two points. There should be a connection between two points and the two points should be continuous to plot a line. In graphs, a point can have two or three axes depending on its dimension.

Suppose, you have two points and they are (x1, y1) = (2, 1) and (x2, y2) = (2, 5). If we continuously connect these two points corresponding to the x-axis and y-axis, then we will get a line. The line plotting has been animated in the below figure.

Plot a line in Graph

Parametric equation of a line

The parametric equation to plot a circle in MatLab is also discussed on this site. The parametric equation of a line is used to generate continuous points between two initial points.

2D parametric equation

x = x₀ + m₁t

y = y₀ + m₂t

3D parametric equation

x = x₀ + m₁t

y = y₀ + m₂t

z = z₀ + m₃t

Slope intercept form of a line

The most non-vertical line generates by the slope-intercept form. In geometry, we are used this line form to draw a line. It is mostly used in the linear regression algorithm. 

y = mx + c

This is the slope-intercept equation of a line. Where x is an independent variable, y is a dependent variable, m is the slope, and c is a constant value. 

What is a vertical line?

A vertical line is a directed line where the value of x is constant. That means the value of the x-axis is the same while the value of the y-axis will be incremented in a given range.

What is a horizontal line?

A horizontal line is a directed line where the value of y is constant. 

What is a straight line?

A straight line is a one-way directed line that is not curved at any point in a line. A straight line can be vertical or horizontal, or diagonal with respect to the x-axis and y-axis.

vertical, horizontal, and diagonal straight line (left to right)

How to plot a line in MatLab?

Plotting a line in MatLab is simple. MatLab provides a pre-defined function to plot a line.

# to plot a 2D line
line(x, y)


# to plot a 3D line
line(x, y, z)

Code to plot a line in MatLab

% point1 = [x1, y1]
point1 = [1, 2];

% point2 = [x2, y2]
point2 = [5, 10];

% ploting the line using the 'line' function of matlab
line(point1,point2)

Output line

Output figure of the above code

How to plot a vertical straight line in MatLab?

You can plot a vertical line in MatLab in three ways. 

1. Plot a vertical line in MatLab using the 'line()' function

code

% x value is constant
x = linspace(2,2);

% y vlaues are independent to increase
y = linspace(3,10);

% plot the x and y values in the 'line()'
line(x,y)

output figure

2. Plot a vertical line in MatLab using 'plot()' function

code

% x value is constant
x = linspace(2,2);

% y vlaues are independent to increase
y = linspace(3,10);

% plot the x and y values in the 'line()'
plot(x,y)
% turn on the grid mode for a clear view
grid on

output figure

The code can be made easier if we write it like this,

% plot([x1, y1], [x2, y2])
plot([1,1], [5,4])

3. Plot a vertical line in MatLab using 'xline()' function

The 'xline()' function of MatLab needs a constant x-axis value to plot a vertical line automatically.

code

xline(2);

output figure

How to plot a horizontal straight line in MatLab?

It is easy to plot a horizontal line in MatLab with a few lines of code like the plot of a vertical line. You need to exchange the x-axis value with the y-axis value. Now, the value of y should be constant to plot a horizontal line in MatLab.

1. Plot a horizontal line in MatLab using the 'line()' function

code

% x value is independent to increase
x = linspace(2,10);

% y vlaue is constant
y = linspace(3,3);

% plot the x and y values in the 'line()'
line(x,y)

output figure

2. Plot a horizontal line in MatLab using 'plot()' function

code

% plot([x1, y1], [x2, y2])
plot([1,4], [5,5])

output figure

3. Plot a horizontal line in MatLab using 'yline()' function

code

yline(5)

output figure