Function output an array

I am trying towrite a function that takes an array of variable size, and calculates the differneces between the 1,2 2,3 3,4 ... inputs and displays as an array (without using the diff function). It keep giving a singular output for the first values but need it to give an array for all. any help would be great.

function [out] = differences(in)

%This function allows an array input and the differences between the array

i=1;

while (i<=size(in))

out(i)= in(i+1)-in(i);

i=i+1;

end

end

Answer 1

[VBBV]

in = [rand(1,15);rand(1,15)];
differences(in)

ans = 1×15

0.2886 -0.0528 0.2459 -0.6453 -0.3648 -0.6805 0.3954 0.1678 0.1278 -0.2929 -0.5549 -0.1945 -0.4947 -0.0121 0.1477

 
function [out] = differences(in)
%This function allows an array input and the differences between the array
i=1;
while (i<size(in,1))
    out(i,:)= in(i+1,:)-in(i,:);
      
    i=i+1;
end
end