how can i draw input rectangular shape with specific iterations

n=100
for k=1:n
    if k<=25 
        r(k)=1 
    elseif  k>25&k<=50
        r(k)=-1
    elseif  k>50&k<=75
        r(k)=1
    else
        r(k)=-1
    end
end
plot (k,r(k))

This appears when running:

But I want this figure:

[Star Strider]

See: how can i draw this figure

[Image Analyst]

In general, you would not use & in that situation (your "if" test), you'd use &&, though in this case it won't matter.

Answer 1

[Star Strider]

sqwv = @(x) 1.*(((x > 0) & (x < 25)) | ((x > 50) & (x < 75))) - 1.*(((x > 25) & (x < 50)) | ((x > 75) & (x < 100)));

x = 0:100;
y = sqwv(x);

figure(1)
plot(x, y,'-b')
axis([0  100    -1.5  1.5])

Answer 2

[Image Analyst]

You can use repmat(), like I do in my attached demo.

Or, if you have the Signal Processing Toolbox, you can use the square() function:

x = square(t,duty) generates a square wave with specified duty cycle, duty, which is a number between 0 and 100. The duty cycle is the percent of the period in which the signal is positive.

[Star Strider]

I did a version of the repmat approach in how can i draw this figure earlier.