CPP - C++ Programming Basics

D and 3-D Plots

• Line Plots

>> x = 0:pi/100:2*pi;

>> y = sin(x);

>> plot(x,y)

>> 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--')

• 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.

>> x = 0:pi/100:2*pi;

>> y = sin(x);

>> plot(x,y)

>> hold on

>> y2 = cos(x);

>> plot(x,y2,':')

>> legend('sin','cos')

• Until you use hold off or close the window, all plots appear in the current figure window.

• 3-D Plots

Three-dimensional plots typically display a surface defined by a function in two variables, z = f(x,y) .

To evaluate z, first create a set of (x,y) points over the domain of the function using meshgrid.

>> [X,Y] = meshgrid(-2:.2:2);

>> Z = X .* exp(-X.^2 - Y.^2);

Then, create a surface plot.

>> surf(X,Y,Z)

• Subplots

The first two inputs to subplot indicate the number of plots in each row and column, The third input specifies which plot is active. For example, create four plots in a 2-by-2 grid within a figure window.

>> t = 0:pi/10:2*pi;

>> [X,Y,Z] = cylinder(4*cos(t));

>> subplot(2,2,1); mesh(X); title('X');

>> subplot(2,2,2); mesh(Y); title('Y');

>> subplot(2,2,3); mesh(Z); title('Z');

>> subplot(2,2,4); mesh(X,Y,Z); title('X,Y,Z');