Matlab Code for Square wave

Hi,

I have to generate a square wave like the one shown in the fig below. Can any one please indicate the appropriate code for that?

Thanks,

[NURRUZAINI MOHD NASIR]

how to generate this coding ?

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/163673-matlab-code-for-square-wave#comment_251311

[Naga Sai]

sir help me how to use this code as userdefinedfunction in matlab

[shreyas kulkarni]

function [z t] = square(n1,n2)

% n1=2 give similar value

% n2=4 give this value

z=[];

t=1:1:n2

x= [];

for i=1:5

for t1= 0.01:0.01:n1

a=1

z=[z a];

x=[x t1]

end

for t2=n1+0.01:0.01:n2

a=-1

z=[z a];

x=[x t2]

end

t=1:0.01:n2;

x=1:0.01:n2;

plot(z);

end

Answer 1

[Image Analyst]

How about repmat()? One of your toolboxes may also have a function.

[Danish Ali]

Repmat command is supposed to be used for multi array declaring. Isn't it? How can it be used to plot a square wave like this one?

[Image Analyst]

No, not really. It's for replicating a matrix vertically and horizontally. Did you look at the help and try it? Did you try anything like this:

% Make one cycle.
oneCycle = [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1];
% Replicate 10 times.
squareWave = repmat(oneCycle, [1, 10]);
% Plot it.
plot(squareWave, 'bo-', 'LineWidth', 2);
grid on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'Outerposition', [0, 0, 1, 1]);

[Danish Ali]

Yeah That worked. Thanks

[Naga Sai]

but it is not like square right

[Naga Sai]

if we use a square function it will be very clear

[Image Analyst]

It is a square wave. From one element to the next, it instantly jumps to the new value. There are no intermediate values - just the high value and the low value, only two values, so it's a square wave.

[Naga Sai]

but that jumping of values should be instant know sir

close all; clear all;

f = 7;
fs = 1000;  
t = 1.5;    
n = [0:1/fs:t];

cycles = t*f;
x = ones(1,length(n));
duty = 50;
oc_samp = fs/f; 
on_samp = (oc_samp * duty)/100;
off_samp = oc_samp - on_samp;

temp = 0;
for i = 1 : ceil(cycles);
    x(temp+on_samp+1:i*oc_samp) = 0;
    temp = temp + oc_samp;

end

plot(n,x(1:length(n)),'LineWidth',2);ylim([-1 1.5]);
% stem(n,x); ylim([-1.5 1.5]);

i think this code is better to get exact square wave

[Image Analyst]

It's basically the same, you just have finer x resolution so when plotted the slopes from low to high appear steeper. Either way, they're both square waves with instantaneous jumps, regardless of how they look while plotted.

[Naga Sai]

thank your sir sir pl help how to generate a square wave without using any functions of matlab with basic functions only

Answer 2

[Ridwan Maassarani]

    %   endCan it be done with this code ?

      t = n*T:1:((n+1)*T);
      %lengtht = length(t);
      % Define x(t) and plot
      if (mod(n,2) == 0)
        %number is even
        x = 1; 
      else
        %number is odd
        x = -1;
      end

      plot(x)
      set(gcf, 'Units', 'Normalized', 'Outerposition', [0, 0, 1, 1]);

[Image Analyst]

No. Evidently not. Just try it.

[Naga Sai]

here n is an undefined function

[Naga Sai]

sir what is n in above function sir please give me an explaination or a code to generate a square wave form without using function

[Image Analyst]

Like I said, this code doesn't work. Did you see my code (now hidden in the comments) with code that DOES work? https://www.mathworks.com/matlabcentral/answers/163673-matlab-code-for-square-wave#comment_251311

% Make one cycle.
oneCycle = [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1];
% Replicate 10 times.
squareWave = repmat(oneCycle, [1, 10]);
% Plot it.
plot(squareWave, 'bo-', 'LineWidth', 2);
grid on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'Outerposition', [0, 0, 1, 1]);

[Naga Sai]

sir help me how to use this code as a function to use it in another program

[Image Analyst]

Do you that you need to know how to use copy and paste? It's control-c and control-v. Or you need help in writing a function? I really don't know what you need help with.

[Naga Sai]

i want this above program to use it as a function to generate a square wave sir

[Naga Sai]

sir how to create a fft function please help me regarding this also sir

[Naga Sai]

sir pl respond to my question sir

[Image Analyst]

"how to create a fft function please help me regarding this also" <=== You don't need to create an fft function. There is an fft() function built into MATLAB.

[Naga Sai]

but i have some restrictions from my guide not to use that function it should be created by own

[Image Analyst]

I'm sure you can find fft() code on the internet somewhere. It should be readily available. Are you able to use that (someone else's low level code)?

[Naga Sai]

sir i am unable to find the code sir please help me in this concern

[Image Analyst]

Learning how to use Google would be a beneficial thing for you. I used it and look what I found:

https://en.wikipedia.org/wiki/Cooley%E2%80%93Tukey_FFT_algorithm#Pseudocode

https://rosettacode.org/wiki/Fast_Fourier_transform

http://web.mit.edu/~emin/www.old/source_code/fft/

There are more if you want them.

[Naga Sai]

Sir please clear the error in this code sir

    function y = MYFFT(x)
a=size(x);
N=a(2);
n=log2(N);
l=1;
N2=N/2;
NU1=n-1;
k=0;
while(l<=n)
 while(k<=N-1)
 I=1;
 while(I<=N2)
 M=fix(k/(2^NU1));
 b=dec2bin(M,n);
 q=seqreverse(b);
 P=bin2dec(q);
 W=exp(-2*i*P*pi/N);
 T1=W*(x(k+1+N2));
 x(k+1+N2)=x(k+1)-T1;
 x(k+1)=x(k+1)+T1;
 k=k+1;
 I=I+1;
 end
 k=k+N2;
 end
end

[Naga Sai]

sir please clear error in above function sir

[Image Analyst]

Please give the link to your source code so I can compare your MATLAB code to the original, which presumably is in pseudocode or another language.

Answer 3

[Daniel Robin]

The following square wave function can be used just like sin(x) providing a phase argument and duty-cycle and getting a signal in the range -1 to 1 accordingly.

function y = square(x, D)
    r = mod(x/(2*pi), 1);    % generate a ramp over every cycle
    y = 1 - 2*(r > D);       % output result from -1 to 1
end