因為案例需要，是以這裡先看一下linspace這個函數的用法：
y = linspace(x1,x2)；
均勻産生位于x1 到 x2 之間的100個點；
y = linspace(x1,x2,n)；
均勻産生位于x1 到 x2 之間的n個點。
generates a square wave with period 2π for the elements of the time array
x
= square(
t
)
. t
square
is similar to the sine function but creates a square wave with values of –1 and 1.
産生一個周期為 2π 的方波信号；
generates a square wave with specified duty cycle
x
= square(
t
,
duty
)
duty
. The duty cycle is the percent of the signal period in which the square wave is positive.
産生一個周期為 2π 的方波信号，duty表示占空比，例如duty = 30，則占空比為30%，也就是正幅度與整個周期的比值。
案例1：在0 到 3π之間等間隔産生100個點，然後産生一個周期為2π的方波
%Create a vector of 100 equally spaced numbers from 0 to 3π. Generate a square wave with a period of 2π.
clear
clc
close all
t = linspace(0, 3*pi);
x = square(t);
plot(t/pi,x,'.-',t/pi,sin(t)); %Plot the square wave and overlay a sine. Normalize the x-axis by .
xlabel('t / \pi')
grid on 
在 -pi 到 2*pi 之間等間隔産生121個點作為時間軸，産生一個幅值為1.15的周期方波，同時在同一幅圖上畫一個正弦波，參數與方波一緻；
%evaluate square(2*t) at 121 equally spaced numbers between -pi and 2*pi .
%Change the amplitude to 1.15 . Plot the wave and overlay a sine with the same parameters.
clear
clc
close all
t = linspace(-pi,2*pi,121);
x = 1.15*square(2*t);
plot(t/pi,x,'.-',t/pi,1.15*sin(2*t))
xlabel('t / \pi')
grid on