How to only collect real part of the cube root

I am having a problem while calculating the cube root in the following code; I am getting an imaginary value of R0, which is not physically possible for the problem! how do I could get the real part only in this problem? please help!

N=50
R= linspace(30e-9,100e-9,N)
Nt= linspace(1e17,1e18,N)
Nd= 5e24

for i= N
    R0(i) =((3*R(i).^2).*(-(Nt(i)./Nd)+(R(i)./3))).^(1/3)
end

Answer 1

[Steven Lord]

Use the nthroot function. With this you can replace your loop with element-wise operators and process your whole vector of data in one nthroot call.

[Anil Kumar]

Thank You steven! i tried your suggestion but could not implement this.Can you demosntrate this fucntion in the above mentioned code? how to use it? Thank you.