Store prime and non-prime numbers

Hi guys! I am trying to determine and store prime and non-prime numbers from 1 to 50.

I have made a programm with a FOR and WHILE loop. However, the programm does not store the values correctly.

I don't know if you could tell where the error is and then solve it.

Thanks!

x=[1:50];
x=x';
jj=0; %index for prime_num
nn=0; %index for nonprime_num
ii=2;
p=[];
np=[];
for i=1:length(x)
    while ii<=sqrt(x(i))
        if rem(x(i),ii)==0
        jj=jj+1;
        p(jj)=x(i);    
        else
            nn=nn+1;
            np(nn)=x(i);
        end
        ii=ii+1;
    end
end

[Davide Masiello]

Could you explain your code in more detail? It seems overly complicated, you could easily do this

N = 1:50;
p = primes(N(end))

p = 1×15

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47

np = N(~any(N==p'))

np = 1×35

1 4 6 8 9 10 12 14 15 16 18 20 21 22 24 25 26 27 28 30 32 33 34 35 36 38 39 40 42 44

[Eustaquio]

Hi Davide!

Well, it is actually a seminar on Matlab for my master's course, and I want to learn basically for and while loops. Actualy, I am not using the prime function (just to make it harder for me and understanding things better).

I don't know if you saw the error on my code?

Even if you didn't, thank you so much!

Answer 1

[Torsten]

x=[1:50];
x=x';
jj=0; %index for prime_num
nn=1; %index for nonprime_num
p=[];
np=[];
np(1) = 1;
for i=2:length(x)
    iprime = 1;
    for ii=2:i/2
      if mod(x(i),ii)==0
        nn=nn+1;
        np(nn) = x(i);
        iprime = 0;
        break
      end
    end
    if iprime == 1
      jj = jj+1;
      p(jj) = x(i);
    end
end
p

p = 1×15

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47

np

np = 1×35

1 4 6 8 9 10 12 14 15 16 18 20 21 22 24 25 26 27 28 30 32 33 34 35 36 38 39 40 42 44

[Eustaquio]

Appreciate it man!

Thank you so much!