Adding zeroes to Row Vector using a script

I wanted to create a script, which would insert "m" amount of zeroes just after every "M-th" element of a given vector, x, to create a new vector. Ie: x = [1 2 3 4 5 6] for instance.

The input would use y = zero_insertion(x,M,m)

Code so far: function y = zero_insertion(x,M,m) a = zeros(1,m) w = x(1:M) y = [w a]

and that will get me a row vector with that has up to the M-th element and the number of "m" zeroes afterwards. However, I just can't figure out how to make a loop to do that for every "M-th" element, and I also can't retrieve the rest of my original vector.

x = [1 2 3 4 5 6] for instance.

Example: If input was y = zero_insertion([1 2 3 4 5 6],1,1) then result would be [1 0 2 0 3 0 4 0 5 0 6 0]

How would I do this? Thanks for your assistance

Answer 1

[Nathaniel]

It would be simple if you guaranteed that numel(x)/M is always an integer, but without that guarantee:

function y = zero_insertion(x,M,m) 
modxm = mod(numel(x),M);
padding = logical(modxm)*M-modxm;
newx = reshape([x NaN(1,padding)],M,[]); 
y1 = [newx ; zeros(m, size(newx,2))]; 
y2 = reshape(y1,1,[]);
y = y2(1:(numel(y2)-logical(padding)*(padding+m)));

Or if you want to keep the zeros even if numel(x)/M isn't an integer, the last line is:

   y = y2(~isnan(y2));

[Ben]

Thanks so much! This is exactly what I needed to create.

Answer 2

[Sean de Wolski]

x2 = zeros(1,2*numel(x)); %thanks Andrei!
x2(1:2:end) = x;

Or:

reshape([x;zeros(size(x))],1,[])

[Andrei Bobrov]

Hi Sean! Small typo

x2 = zeros(1,2*numel(x));

x2(1:2:end) = x;

[Sean de Wolski]

yup, thanks Andrei!