plot square-wave sine grating

Hello,

I would like to plot several different black and white stripe patterns with different sine-wave frequencies.

So far I have figured out how to make a sine grating, however, I can't seem to determine how to go about changing this frequency grating to a square wave (code below).

Here is waht a get vs. what I want (pic from the internet)

vs

Any advice for how to do this will be greatly appreciated!

frequency = 10;
phase = 90;
amplitude = 1;
[X,Y]=meshgrid(0:0.001:1,0:0.001:1);
% X = square(X);
Z = amplitude*sin((2*3.1415*frequency.*X)+(phase));
surf(X,Y,Z)
shading interp
view(0,90)
colormap gray
axis off
axis square 

Answer 1

[Star Strider]

To change a sine wave to a square wave, use the sign function:

t = linspace(0, 5, 250);
f = 2;
sinwav = sin(2*pi*t*f);
sqrwav = sign(sin(2*pi*t*f));

figure
plot(t, sinwav)
hold on
plot(t, sqrwav)
hold off
grid
ylim(ylim*1.1)

EDIT — (10 Nov 2020 at 00:14)

Adapting this to your code:

frequency = 10;
phase = 90;
amplitude = 1;
[X,Y]=meshgrid(0:0.001:1,0:0.001:1);
% X = square(X);
Z = amplitude*sign(sin((2*3.1415*frequency.*X)+(phase)));
surf(X,Y,Z)
shading interp
view(0,90)
colormap gray
axis off
axis square 

producing this plot:

.

[Kate Feller]

doh! so simple! I suppose i just don't know what I don't know.

Thank you so much!

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

.

Answer 2

[Setsuna Yuuki.]

t = 85:1e-2:100;
[X,Y]=meshgrid(t);
% you can use fourier series to see the change in the function 
% components = 1 --> sinusoidal wave (Figure 1)
% components = 5 -- Figure 2
% components ~ 100 --> square wave (Figure 3)
components = 100; sumatoria = 0 ;
for k = 1:1:components
    n = 2*k-1;
    serie=2/pi*1/n*sin(n*pi*t);
    sumatoria = serie+sumatoria;
end
    signal = 1/2+sumatoria;

Z = signal.*X;
figure
surf(X,Y,Z)
shading interp
view(0,90)
colormap gray
axis off
axis square 

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