Passing vector argument into a function returns only one value

Hello,

I am trying to create a unit step function without the 0.5 at n = 0, to use within a bigger script. However I cannot input a simple 1D vector into it.

function [a] = ustep(n)
    if n<0
        a=0;
    else
        a=1;
    end
end

And now this trial code, in which I try to pass -100:100 vector to it, in order to test it. I have useless variables just for testing purposes.

clear; close all; clc;

n = [-100:100];
signal = ustep(n);
signal1 = ustep(0:100);

stem(ustep(n));

stem(n, ustep(n)) straight up doesn't work because ustep() with a vector argument just returns 1. Which is not as sizeable as -100:100 obviously.

Answer 1

[David Hill]

function [a] = ustep(n)
  a=zeros(size(n));
  a(n>=0)=1;
end

[jack]

Thank you very much this works beautifully. But could you please explain why the above code doesnt work? Is it because of if statements?

[David Hill]

Several problems. When you set a=1 or a=0 your answer will always be scalar (1 or 0). n<0 provides an array of logical 1's and 0's depending on the values in n.

function [a] = ustep(n)
  a=n>=0;%This will give you the same thing but with logicals
end

[Stephen23]

"Is it because of if statements?"

Yes: if you must use an IF statement on individual elements of an input array, then you would need to nest the IF inside a loop (iterating over the elements of the input array, and using appropriate indexing on the input and output arrays).

However it is much simpler to basic MATLAB vectorized operations, as David Hill showed.