How to pull out numbers from a vector in matlab?

I am having trouble figuring out how to extract certain points out of the vector I create.  The point of this problem is to create a function that finds the first nth prime numbers without using native matlab functions.  I create a large matrix that I narrow down to create one that has a large number of prime numbers.  Then out of that function I pull out the first n prime numbers.  I keep getting an error that says "Index exceeds matrix dimensions.".  Any help would be great. The function is below:

function [ prime ] = HW01_problem_07( n )

%UNTITLED Summary of this function goes here

%   Detailed explanation goes here

N=10*n;

array = 2:N;

prime=[];

for i = 1:length(array)

    if array(i) ~= 0 

        for j = i+2: length(array) 

            if mod(array(j), array(i)) == 0 

            array(j) = 0; 

            end 

        end 

    end 

        if array(i) ~= 0 

          prime(length(prime) + 1) = array(i);

          prime=prime(1:n);

          

        end

        

end

Answer 1

[Walter Roberson]

          prime=prime(1:n);

needs to go after the "for" loop.