Changing prime numbers in a matrix

I printed a 100x100 random matrix of integers from 1 to 50. However, I want to replace the prime numbers in this matrix with the number 1415. How can I replace the prime numbers in that matrix with a specific number (1415)? Thank you.

Answer 1

[Scott MacKenzie]

M = randi([1 50],100);
M(isprime(M)) = 1415;

[Doga Ince]

Thank you but i am getting error 😥

Could I be getting an error because I want to both find the prime numbers in my matrix and replace those numbers with 1415? Can you help me?

[Scott MacKenzie]

Ok, sure. This modification stores the locations of the prime numbers in a logical variable, outputs the prime numbers, then replaces the prime numbers in M with 1415.

M = randi([1 50],100);

% find locations in M containing prime number
primeLogical = isprime(M);

% output prime numbers in M
M(primeLogical)

% change prime numbers in M to 1415
M(primeLogical) = 1415;