how to use two for loop in one matlab program

for z=1:3
    v(z) = zeros(1,length(x));
    for ii = 1:numel(x)
        V = roots([S0(ii),-S1(ii),S2(ii),-S3(ii)]);
        v(z)(ii) = sqrt((V(z,1))./p);
    end
end

Answer 1

[M]

You should read this:

https://mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

You cannot write v(z)(ii) but you should consider 2 dimensional data and acces it using v(z,ii).