How to show non prime numbers (what is the contrari function of prime?)

Question

Toni Clares 2016-10-9

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/306470-how-to-show-non-prime-numbers-what-is-the-contrari-function-of-prime

编辑： Walter Roberson 2016-10-9

clc
clear all
n=input('number')                 % Natural number that you want to know if it a prime number
i=2;
x=[];
if n==0 | n==1
    disp('there are not prime numbers');
end
while i<=sqrt(n)
      if rem(n,i)==0    %In this part i want to show the non prime numbers (i don't know the function name)     
          x=n
      else              %In this part i show the prime numbers
          y=primes(n)
          break
      end
      i=i+1;
  end
fid=fopen('Prime_numbers.txt','w');    %In this final part i create a .txt document for save the prime       
fprintf(fid,'%2d\t%2g\t',y);
fclose(fid);
fid=fopen('Non_prime_numbers.txt','w'); %In this final part i create a .txt document for save the non prime 
fprintf(fid,'%2d\t%2g\t',x);
fclose(fid);

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Answer 1

Walter Roberson 2016-10-9

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/306470-how-to-show-non-prime-numbers-what-is-the-contrari-function-of-prime#answer_238213

You could use setdiff() of the range of values, asking to remove the primes.

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Toni Clares 2016-10-9

编辑：Walter Roberson 2016-10-9

在 MATLAB Online 中打开

%Thanks i tried but i don't know the right way to use it

clc
clear all
n=input('number')                 % Natural number that you want to know if it a prime number
i=2;
x=[];
if n==0 | n==1
    x=n;
end
while i<=sqrt(n)
      if rem(n,i)==0
          x=n
      else
          z=1:n
          y=primes(n)
          x=setfdiff(z,y)  % I don't know how to use it
          break
      end
      i=i+1;
  end
fid=fopen('Prime_numbers.txt','w');
fprintf(fid,'%2d\t%2g\t',y);
fclose(fid);
fid=fopen('Non_prime_numbers.txt','w');
fprintf(fid,'%2d\t%2g\t',x);
fclose(fid);

Toni Clares 2016-10-9

编辑：Walter Roberson 2016-10-9

在 MATLAB Online 中打开

I sort out!!!

clc
clear all
n=input('number')                 % Natural number that you want to know if it a prime number
i=2;
x=[];
if n==0 | n==1
    x=n;
end
z=1:n;
y=primes(n)
x=setdiff(z,y)
fid=fopen('Prime_numbers.txt','w');
fprintf(fid,'%2d\t%2g\t',y);
fclose(fid);
fid=fopen('Non_prime_numbers.txt','w');
fprintf(fid,'%2d\t%2g\t',x);
fclose(fid);