Prime number or its nearest prime numbers

on 13 Apr 2012

Andrei Bobrov (view profile)

anyone please tell me in matlab how to write a function to find prime number of any number if it is not prime number then function show its nearest prime numbers... let take example ...take number 9 we know it is not prime then the program will show its nearest prime like 7 and 11..

Thomas

Thomas (view profile)

on 13 Apr 2012

if this is homework, can you show, what you have done so far?

Jan Simon

Jan Simon (view profile)

on 13 Apr 2012

What have you tried so far and which problem occurred?

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Andrei Bobrov (view profile)

on 13 Apr 2012

input x

```x = 24;
```

solution

```X = [x x];
out = zeros(1,2);
while 1
t = isprime(X);
if all(t)
out = X;
break
elseif any(t)
out(t) = X(t);
t1 = ~t;
X(t1) = X(t1) - sum([1 -1].*t1);
else
X = X - [1 -1];
end
end
out = unique(X)
```

Jan Simon

Jan Simon (view profile)

on 13 Apr 2012

I assume, this is the solution of Rahul's homework, Andrei.

Rahul Singh

Rahul Singh (view profile)

on 14 Apr 2012

thanks Andrei Bobrov........i think this is useful answer for me............

on 13 Apr 2012