2-D and 3-D Plots

Line Plots

To create two-dimensional line plots, use the plot function. For example, plot the sine function over a linearly spaced vector of values from 0 to $$2\pi$$:

x = linspace(0,2*pi);
y = sin(x);
plot(x,y)

You can label the axes and add a title.

xlabel("x")
ylabel("sin(x)")
title("Plot of the Sine Function")

By adding a third input argument to the plot function, you can plot the same variables using a red dashed line.

plot(x,y,"r--")

"r--" is a line specification. Each specification can include characters for the line color, style, and marker. A marker is a symbol that appears at each plotted data point, such as a +, o, or *. For example, "g:*" requests a dotted green line with * markers.

Notice that the titles and labels that you defined for the first plot are no longer in the current figure window. By default, MATLAB® clears the figure each time you call a plotting function, resetting the axes and other elements to prepare the new plot.

To add plots to an existing figure, use hold on. Until you use hold off or close the window, all plots appear in the current figure window.

x = linspace(0,2*pi);
y = sin(x);
plot(x,y)

hold on

y2 = cos(x);
plot(x,y2,":")
legend("sin","cos")

hold off

3-D Plots

Three-dimensional plots typically display a surface defined by a function in two variables, $$z=f(x,y)$$. For instance, calculate $$z=x{e}^{-x^2-y^2}$$ given row and column vectors x and y with 20 points each in the range [-2,2].

x = linspace(-2,2,20);
y = x';
z = x .* exp(-x.^2 - y.^2);

Then, create a surface plot.

surf(x,y,z)

Both the surf function and its companion mesh display surfaces in three dimensions. surf displays both the connecting lines and the faces of the surface in color. mesh produces wireframe surfaces that color only the connecting lines.

Multiple Plots

You can display multiple plots in different parts of the same window using either tiledlayout or subplot.

The tiledlayout function was introduced in R2019b and provides more control over labels and spacing than subplot. For example, create a 2-by-2 layout within a figure window. Then, call nexttile each time you want a plot to appear in the next region.

t = tiledlayout(2,2);
title(t,"Trigonometric Functions")
x = linspace(0,30);

nexttile
plot(x,sin(x))
title("Sine")

nexttile
plot(x,cos(x))
title("Cosine")

nexttile
plot(x,tan(x))
title("Tangent")

nexttile
plot(x,sec(x))
title("Secant")

If you are using a release earlier than R2019b, see subplot.

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