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

2015 5 28
3 个回答
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更新时间：2015 8 20
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0 个投票

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
Feedback: Your function made an error for argument(s) 2
Your solution is _not_ correct.
Guide me where i need corrections in my code. Thanks in advance for assistance..

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Ryan Livingston
Ryan Livingston 2015-5-28
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.

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 采纳的回答

Andrei Bobrov
Andrei Bobrov 2015-5-28

0 个投票

function p = myprime(n)
p = n-nnz(rem(n,1:n)) == 2;

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@Andrei thanks for contributions... Please mark comments in 2nd line of your code so that i can understand what is actual manipulating here
Andrei Bobrov
Andrei Bobrov 2015-5-29
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

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更多回答（2 个）

B.k Sumedha
B.k Sumedha 2015-5-28

0 个投票

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.

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@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
Feedback: Your function made an error for argument(s) 4
Your solution is _not_ correct.

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charu sharma
charu sharma 2015-8-20

0 个投票

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

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