Array of N prime numbers

Question

Leandro Cavalheiro 2016-6-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/292316-array-of-n-prime-numbers

评论： Gangga Fardede 2017-10-30

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Hello. I'm new to MatLab. I've just written a code to identify if a given number N is a prime number.

Basically, that's it:

function [out] = myIsPrime(n)
if n == 1
      out = 0;
elseif n == 2
      out = 1;
elseif all(rem(n,2:n-1) ~= 0)
      out = 1;
else
     out = 0;
end
end

Now I want my output to be the first 'N' prime numbers counting from 2 and up.

I've been trying for hours but my brain is just frozen. How do I do that using if, for or while loops?

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Gangga Fardede 2017-10-30

I want to ask, how to make a row, if we input number, the output will display prime number have a lot of n Like we input '4' abd will dispay '2 3 5 7'

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Answer 1

Walter Roberson 2016-6-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/292316-array-of-n-prime-numbers#answer_226766

while the count of primes found is less than your target count, keep trying the next number in sequence to determine whether it is prime; if it is then increment the count of primes found and store the prime in your array.

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Walter Roberson 2016-6-26

在 MATLAB Online 中打开

   num_primes_found = num_primes_found + 1;
   list_of_primes(num_primes_found) = the_candidate_number;

To store only N numbers, use a while loop on num_primes_found

Leandro Cavalheiro 2016-6-26

编辑：Walter Roberson 2016-6-26

在 MATLAB Online 中打开

I made it!

function [primes] = myNPrimes(N)
primes = 0;
k = 0;
f = 0;
while size(primes,2) < N
    k = k + 1;
      if k == 1
          out = 0;
      elseif k == 2
          out = 1;
      elseif all(rem(k,2:k-1) ~= 0)
          out = 1;
      else
          out = 0;
      end
      if out == 1
          f = f+1;
          primes(f) = k;
      end
  end
  end