contour plots in MATLAB

Introduction

Contour plots help us see how values change over a 2D area using lines. They make it easy to understand patterns and shapes in data.

To visualize elevation on a map, like hills and valleys.

To show temperature changes across a surface.

To understand pressure or density variations in physics or engineering.

To explore how two variables affect a third one in experiments.

Syntax

MATLAB

contour(X, Y, Z)
contour(X, Y, Z, levels)
contour(X, Y, Z, 'LineWidth', value)
contour(X, Y, Z, 'LineColor', color)

X and Y are matrices or vectors defining grid points.

Z is a matrix of values at each (X, Y) point.

Examples

Basic contour plot showing curves of constant Z values.

MATLAB

x = 1:5;
y = 1:5;
[X, Y] = meshgrid(x, y);
Z = X.^2 + Y.^2;
contour(X, Y, Z);

Draw contour plot with exactly 10 contour lines.

MATLAB

contour(X, Y, Z, 10);

Make contour lines thicker for better visibility.

MATLAB

contour(X, Y, Z, 'LineWidth', 2);

Sample Program

This program creates a smooth contour plot of a Gaussian hill. It uses 15 contour lines and thicker lines for clarity. Labels and title help understand the plot.

MATLAB

x = linspace(-2, 2, 50);
y = linspace(-2, 2, 50);
[X, Y] = meshgrid(x, y);
Z = exp(-X.^2 - Y.^2);
contour(X, Y, Z, 15, 'LineWidth', 1.5);
title('Contour plot of Gaussian function');
xlabel('X axis');
ylabel('Y axis');

Important Notes

You can add labels on contour lines using clabel function after contour.

Use meshgrid to create grid points for X and Y.

Contour plots work best with smooth data for clear lines.

Summary

Contour plots show lines of equal values on a 2D grid.

Use contour with grid data X, Y and values Z.

You can control number of lines and line style for better visuals.