Put Number Calculated in Legend Matlab

MATLAB's plotting functions allow you to create informative visualizations, and one of the key elements is the legend. This guide explains how to add numbers calculated in the legend to enhance your MATLAB plots with precise data representation.

Introduction

The legend in MATLAB plots serves as a key to identify different data series. While MATLAB automatically generates legends, you can enhance them by adding calculated numbers directly to the legend entries. This technique is particularly useful when you want to display calculated statistics or values alongside the plot lines.

In this guide, you'll learn how to:

Create a basic MATLAB legend
Add calculated numbers to legend entries
Customize the legend appearance

Basic MATLAB Legend

Before adding calculated numbers, let's review how to create a basic legend in MATLAB. The legend function is used to add a legend to a plot.

Basic Legend Syntax:

legend('Series 1', 'Series 2', ...)

Here's a simple example:

x = 0:pi/100:2*pi;
y1 = sin(x);
y2 = cos(x);
plot(x, y1, x, y2);
legend('sin(x)', 'cos(x)');

This creates a plot with two curves and a legend identifying each curve.

Adding Numbers to Legend

To add calculated numbers to legend entries, you can use string formatting to include the values in the legend labels. MATLAB's sprintf function is particularly useful for this purpose.

Adding Numbers to Legend:

% Calculate values
mean_y1 = mean(y1);
mean_y2 = mean(y2);

% Create legend with formatted strings
legend(sprintf('sin(x) (Mean: %.2f)', mean_y1), ...
       sprintf('cos(x) (Mean: %.2f)', mean_y2));

This example calculates the mean values of each data series and includes them in the legend entries with two decimal places.

Tip: You can use any calculated value in the legend, not just means. Common calculations include maximum, minimum, standard deviation, or any custom formula you've applied to your data.

Customizing Legend Appearance

MATLAB provides several options to customize the appearance of your legend:

Location - Position the legend in different corners
FontSize - Adjust text size
Box - Control whether the legend has a border
Orientation - Display legend vertically or horizontally

Custom Legend Example:

legend('sin(x)', 'cos(x)', ...
               'Location', 'northwest', ...
               'FontSize', 12, ...
               'Box', 'off', ...
               'Orientation', 'vertical');

These customization options help make your legend more readable and visually appealing.

FAQ

Can I add multiple calculated values to a single legend entry?: Yes, you can combine multiple calculated values in a single legend entry by formatting the string accordingly. For example: sprintf('sin(x) (Mean: %.2f, Max: %.2f)', mean_y1, max_y1).
How do I change the number of decimal places in the legend?: Use the format specifier in sprintf. For example, %.3f displays three decimal places, while %.0f displays no decimal places.
Can I add units to the calculated values in the legend?: Yes, simply include the units in the string. For example: sprintf('sin(x) (Mean: %.2f m)', mean_y1).
How do I remove the legend from a plot?: Use the legend('off') command to remove the legend from a plot.
Can I create a legend for a 3D plot?: Yes, the legend function works similarly for 3D plots. Just ensure you're working with the correct figure and axes.