how to make a function that take an integer as input and return ture if this prime otherwise false

83 views (last 30 days)
Muhammad Usman Saleem on 28 May 2015
Answered: charu sharma on 20 Aug 2015
Hi everyone; I am going to attempt that question: Write a function myprime that takes n, a positive integer, as an input and returns true if n is prime or returns false otherwise. Do not use the isprime or primes or factor built-­‐in functions. Hint: you can use the rem or fix functions. I am using that code
function prime=myprime(n)
a=abs(n);
i=1;
while i<a
if rem(a,i)~=0
prime='TURE';
else
prime='FALSE';
end
i=i+1;
end
end
and getting error
Guide me where i need corrections in my code. Thanks in advance for assistance..
Ryan Livingston on 28 May 2015
I removed the product tag for "MATLAB Coder" below since this example is not using the product MATLAB Coder. Please only use that product tag when this product is involved. Thank you.

Andrei Bobrov on 28 May 2015
function p = myprime(n)
p = n-nnz(rem(n,1:n)) == 2;
Andrei Bobrov on 29 May 2015
a = rem(n,1:n) % determining the remainder of division n on a series of numbers 1: n
b = nnz (a); % the number of divisions with remainder
out = n-2 == b; % condition for prime number

B.k Sumedha on 28 May 2015
function result = isprime2(number)
number=5;
result=true;
%%check if number is a nonnegative integer
if floor(number)~=number || number<0
result=false;
return
end
%%check if number can be divided by another integer
for k=2:(number/2)
if rem(number,k)==0
result=false;
return
end
end
Returns 1 if the number isprime and returns 0 if the number is not prime.
Muhammad Usman Saleem on 28 May 2015
@B.k Sumedha thanks for contribution i am now using that code
function result = myprime(n)
n=5;
result=true;
if floor(n)~=n || n<0
result=false;
return
end
for k=2:(n/2)
if rem(n,k)==0
result=false;
return
end
end
but when i test this code i got an error
Feedback: Your function performed correctly for argument(s) 2
Feedback: Your function performed correctly for argument(s) 3

charu sharma on 20 Aug 2015
For number n being prime, if it is divisible by any of the numbers from 2 to n/2 then it is not prime so you just need to check the divisibility till n/2. MATLAB uses 0 or 1 in place of false and true. You can refer this too for less time complexity: http://farzicoders.blogspot.in/2015/08/write-function-myprime-that-takes-n.html