MATLAB Contour Plots

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Contour plots are a powerful visualization tool for two-dimensional data, often used to represent the relationship between three variables on a two-dimensional plane. In MATLAB, contour plots can be created using the contour and contourf functions. This article will show you how to create and customize contour plots to suit your needs.

Creating Contour Plots

To create a contour plot in MATLAB, you need a matrix containing the data you want to visualize. The rows and columns of the matrix represent different values of the X and Y variables, while the matrix's elements represent the corresponding values of the Z variable. Here's an example:

% Define the X and Y variables
x = linspace(-2*pi, 2*pi, 100);
y = linspace(-2*pi, 2*pi, 100);

% Create the X-Y grid
[X, Y] = meshgrid(x, y);

% Calculate the Z variable (for example, sine of the distance from the origin)
Z = sin(sqrt(X.^2 + Y.^2));

% Generate the contour plot
contour(X, Y, Z)

This code generates a contour plot of the sine function applied to the distance from the origin on a grid covering a range of -2π to 2π in both X and Y directions.

Filled Contour Plots

A filled contour plot, or contour map, is similar to a regular contour plot, but the regions between the contour lines are filled with colors to better visualize the data. In MATLAB, you can create a filled contour plot using the contourf function:

contourf(X, Y, Z)

Customizing Contour Plots

MATLAB provides various options to customize your contour plots. You can change the number of contour lines, their color, and the color map used for filled contour plots. Let's explore some of these options.

Changing the Number of Contour Lines

By default, MATLAB chooses the number of contour levels automatically. You can specify the number of contour lines by adding a parameter to the contour or contourf function:

% Display 20 contour lines
contour(X, Y, Z, 20)

% Display 10 filled contour lines
contourf(X, Y, Z, 10)

Changing Contour Line Colors

By default, MATLAB uses a consistent color for all contour lines. You can change the color of the contour lines by setting the LineColor property:

% Change contour line color to red
contour(X, Y, Z, 'LineColor', 'red')

Changing the Color Map

For filled contour plots, MATLAB uses a default color map to fill the regions between contour lines. You can change the color map using the colormap function:

% Create a filled contour plot
contourf(X, Y, Z)

% Change the color map to 'jet'
colormap('jet')

MATLAB offers many built-in color maps, such as 'parula', 'jet', and 'hsv'. You can also create custom color maps.

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