Problem 14. Find the numeric mean of the prime numbers in a matrix.

Created by Cody Team

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There will always be at least one prime in the matrix.

Example:

 Input  in = [ 8 3
               5 9 ]
 Output out is 4 or (3+5)/2

Solve

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Last Solution submitted on Oct 20, 2025

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the cyclist on 26 Jan 2012

2 is prime, so the example solution should be (2+3+5)/3 = 3.33....

... on 25 Feb 2012

+1, the example is wrong :(

Ned Gulley on 27 Mar 2012

*blushing* Oops! At least we got the actual test suite right. Thanks for the notes. Fixed it.

Hassan Javaid on 5 Aug 2013

i didn't understand the problem

Hemanth on 1 Nov 2013

good one...

wayne jackson on 6 May 2014

I don't understand why this doesn't work for test 3: out=sum(in.*isprime(in))/sum(isprime(in))
it works for all other tests but test 3 requires an answer of 3 and the code gives an answer of 3.0000. Can anyone tell me why?

Khairul Bashar Syed on 17 Jul 2014

funny :)

Suraj Mankulangara on 21 Feb 2018

good

Prajith Chilummula on 18 Apr 2018

Good one

Mehran Akbari on 11 Feb 2020

The question topic is hard to understand.

Suraj Kumar on 26 Jul 2020

Good Problem for beginners.

Leo S on 30 Nov 2020

What is wrong with

a = find( isprime( in))
out = mean( in( a)) ?

It works perfectly in my own MATLAB environment

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Problem 14. Find the numeric mean of the prime numbers in a matrix.

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Problem 14. Find the numeric mean of the prime numbers in a matrix.

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