【 MATLAB 】legend 的使用简析
目录
MATLAB 中 legend 可以翻译为图例，下面逐一用例子来说明 legend 的用法，并辅以必要的说明。
我只挑选几种使用的来说明。
legend
在作图命令中（plot）给出图例标签；
Plot two lines. Specify the legend labels during the plotting commands by setting the DisplayName property to the desired text. Then, add a legend.
画两条线。 通过将DisplayName属性设置为所需文本，在绘图命令期间指定图例标签。 然后，添加一个图例（legend）。
% Plot two lines.
% Specify the legend labels during the plotting commands by setting the DisplayName property to the desired text.
% Then, add a legend.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
plot(x,y1,'DisplayName','cos(x)')
hold on
y2 = cos(2*x);
plot(x,y2,'DisplayName','cos(2x)')
hold off
legend对代码做如下改动，将两幅图分开画，然后添加图例的方法：
% Plot two lines.
% Specify the legend labels during the plotting commands by setting the DisplayName property to the desired text.
% Then, add a legend.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
subplot(2,1,1);
plot(x,y1,'DisplayName','cos(x)')
legend
%hold on
y2 = cos(2*x);
subplot(2,1,2);
plot(x,y2,'DisplayName','cos(2x)')
% hold off
legendlegend(label1,...,labelN)
label1,...,labelN)给当前轴添加图例；
legend( sets the legend labels. Specify the labels as a list of character vectors or strings, such as label1,...,labelN)legend('Jan','Feb','Mar').
legend（label1，...，labelN）设置图例标签。 将标签指定为字符向量或字符串列表，例如legend（'Jan'，'Feb'，'Mar'）。
绘制两条线并在当前轴上添加图例。 将图例标签指定为图例功能的输入参数。
% Plot two lines and add a legend to the current axes.
% Specify the legend labels as input arguments to the legend function.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
plot(x,y1)
hold on
y2 = cos(2*x);
plot(x,y2)
legend('cos(x)','cos(2x)')将程序稍作改动，将这两个正弦函数的图像画在不同的子图中，并添加标签：
% Plot two lines and add a legend to the current axes.
% Specify the legend labels as input arguments to the legend function.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
subplot(2,1,1);
plot(x,y1)
legend('cos(x)')
% hold on
y2 = cos(2*x);
subplot(2,1,2);
plot(x,y2)
legend('cos(2x)')legend(target,___)
给特定轴添加图例；
% Create a figure with two subplots and return the two Axes objects, ax1 and ax2.
% Plot random data in each subplot. Add a legend to the upper subplot by specifying ax1 as the first input argument to legend.
clear
clc
close all
x = linspace(0,pi);
y1 = rand(3);
ax1 = subplot(2,1,1);
plot(y1)
y2 = rand(5);
ax2 = subplot(2,1,2);
plot(y2)
legend(ax1,{'Line 1','Line 2','Line 3'})
legend(subset,___)
给部分函数添加图例；
subset 是子集的意思，它表示只给这个子集中的函数添加图例，后面的——表示，这些图例的标签，即它们的名字是什么？
下面给出一个实例，参考起来很容易理解：
% If you do not want to include all of the plotted graphics objects in the legend,
% then you can specify the graphics objects that you want to include.
% Plot three lines and return the Line objects created.
% Create a legend that includes only two of the lines.
% Specify the first input argument as a vector of the Line objects to include.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
p1 = plot(x,y1);
hold on
y2 = cos(2*x);
p2 = plot(x,y2);
y3 = cos(3*x);
p3 = plot(x,y3);
hold off
legend([p1 p3],{'cos(x)','cos(3x)'})legend(___,'Location',lcn)
指定图例的位置（方向）以及显示的列数；
% Plot four lines. Create a legend in the northwest area of the axes.
% Specify the number of legend columns using the NumColumns property.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
plot(x,y1)
hold on
y2 = cos(2*x);
plot(x,y2)
y3 = cos(3*x);
plot(x,y3)
y4 = cos(4*x);
plot(x,y4)
hold off
legend({'cos(x)','cos(2x)','cos(3x)','cos(4x)'},'Location','northwest','NumColumns',2)
lgd = legend(___)
给图例添加标题；
% Plot two lines and create a legend. Then, add a title to the legend.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
plot(x,y1)
hold on
y2 = cos(2*x);
plot(x,y2)
hold off
lgd = legend('cos(x)','cos(2x)');
title(lgd,'My Legend Title')
legend('boxoff')
去除图例边框；
% Plot two lines and create a legend in the lower left corner of the axes.
% Then, remove the legend background and outline.
clear
clc
close all
x = linspace(0,pi);
y1 = cos(x);
plot(x,y1)
hold on
y2 = cos(2*x);
plot(x,y2)
hold off
legend({'cos(x)','cos(2x)'},'Location','southwest')
legend('boxoff')Modify Legend Appearance
修改图例的外观；
% Modify the legend appearance by setting Legend properties.
clear
clc
close all
rdm = rand(4);
plot(rdm)
lgd = legend({'Line 1','Line 2','Line 3','Line 4'},'FontSize',12,'TextColor','blue')当然也可以通过下面的方式来修改：
% Modify the legend appearance by setting Legend properties.
clear
clc
close all
rdm = rand(4);
plot(rdm)
lgd = legend('Line 1','Line 2','Line 3','Line 4');
lgd.FontSize = 12;
lgd.TextColor = 'blue';效果是一样的。
下面多改几下：
% Modify the legend appearance by setting Legend properties.
clear
clc
close all
rdm = rand(4);
plot(rdm)
lgd = legend('Line 1','Line 2','Line 3','Line 4');
lgd.FontSize = 12;
lgd.TextColor = 'blue';
lgd.NumColumns = 2;
lgd.Location = 'southwest';
leg.Orientation = 'vertical';
title(lgd,'My Legend Title');