How do I add 0 after every value in a vektor

So i have to add 0 after every value in a vektor. The vektor is decided by the user and im trying to use 'for' in the solution.

for example if my vektor is v=[3,5,2,7] the new vektor should be u=[3,0,5,0,2,0,7,0]

what ive come up with so far, i don't know how to use the 'for' command and im trying to learn

v=input('add a vektor of your choosing: ');

u=zeros(1,2*length(v));

for

????

????

end

disp(['The new vektor is [' num2str(u) ']'])

so far i tried replacing the ?? with

n=1:2:length(v);

v(n)=u;

but got the error msg "Unable to perform assignment because the left and right sides have a different number of elements."

[Walter Roberson]

Hint:

v(1) gets written to u(1)

v(2) gets written to u(3)

v(3) gets written to u(5)

so each increment by 1 in the index of v, results in an increment by 2 in the index of u

u(2*n + something) = v(n)

Answer 1

[Image Analyst]

Try this:

v=[3,5,2,7]; 
for k = 1 : length(v)
    index = (k-1) * 2 + 1;
    u(index) = v(k);
end
% Add final trailing 0
u(end+1) = 0 % Show in command window.

u = 1×8

3 0 5 0 2 0 7 0

[Luqas Lundahl]

That worked! Thank you so much!

Answer 2

[Jan]

This works without a loop.

v = [3,5,2,7];

Now append a 2nd row with zeros:

v = [v; zeros(size(v))];
% Or equivalently:
v(2, :) = 0;

Remember, that Matlab stores values of arrays in column order. Then:

v(:)

is almost what you want to get. Just transpose it.

Alternative is to create a vectore of zeros in the wanted length:

w = zeros(1, numel(v) * 2);

Now fill the indices 1:2:numel(w) with the elements of v. There is no need for a loop and your "n=1:2:length(v); v(n)=u;" is almost correct.

[Luqas Lundahl]

Thanks you for the answer! However, I'm specifically using 'for' because i want to learn how it works so i can use it more efficiently in the future, so i want my code to include it! If you can help me i would really appriciate it!