MATLAB Programming 51 - how to draw contour

A contour line of a function of two variables is a curve along which the function has a constant value. Contour lines are used for creating contour maps by joining points of equal elevation above a given level, such as mean sea level.

MATLAB provides a contour function for drawing contour maps.

Example

Let us generate a contour map that shows the contour lines for a given function g = f(x, y). This function has two variables. So, we will have to generate two independent variables, i.e., two data sets x and y. This is done by calling the meshgrid command.

The meshgrid command is used for generating a matrix of elements that give the range over x and y along with the specification of increment in each case.

Use the meshgrid function to generate matrices X and Y. Create a third matrix, Z, and plot its contours.

x = linspace(-2*pi,2*pi);
y = linspace(0,4*pi);
[X,Y] = meshgrid(x,y);
Z = sin(X)+cos(Y);

figure
contour(X,Y,Z)