Hello! How can I make MATLAB return the smallest, positive, purely real value from a column matrix?

Hello, I would like to know how to make MATLAB return the smallest, positive, purely real value from a column matrix of length n which may contain complex and negative numbers.

So I already know how to get the length of the column matrix. In my case, the column matrix, (Uf), is made from the roots of a polynomial called T3. i.e.

Uf = roots(T3);

The polynomial, T3, is made up of convolutes of other polynomials which I have written in matrix form. If I input certain values for those smaller polynomials, the following function will not return the smallest positive value, and doesn't even know what the variable U_flutter is.

i = 1;
j = 0;

while i<=length(Uf);
    notcomplex = isreal(Uf(i,1));
    if notcomplex == 1 && Uf(i,1)>=0;
        Ufl = Uf(i,1);
        if Ufl < j;            
            U_flutter = Ufl;
        else
            j = Ufl; 
        end
    else
       if Uf(i,1)>0
       U_flutter = j;
       end
    end
    i = i + 1;
end

Thanks!

Answer 1

[Matt Fig]

Uf = [0.84888 +    0.74301i
      -1
      0.31434 +     1.1736i
      0.31434 -     1.1736i
      3
      -0.40027 -     1.2365i
      -0.78795 +    0.20233i
      5]

% Get the smallest, real, positive value if there is one.
idx = imag(Uf)==0 & real(Uf)>0;
sv = min(Uf(idx))

[Neil Chambers]

This is very clever! Thank you!