Question

In MATLAB, ask the user to input a matrix of any size. Ensure that the user inputs a positive, integer matrix. If there is an incorrect input, ask them for a matrix again. Use Loops to do this.

Using loops, find the sum of all prime numbers present in the user-entered matrix. You must not use the built-in isprime function to do this. Use loops. (The number 1 may count as as a prime number)

Example Matrix: [1 2 3; 4 5 6; 7 8 9]

Answer 1

a = input("Enter a matrix:\n"); % taking user input for the first time

while numel(a ( a < 0 )) > 0 % if negative numbers are in, asking again
a = input("Enter a matrix whithout negative numbers:\n");
end

[rows cols] = size(a); % taking size of the matrix

sum = 0;

for i = 1:rows % looping through rows
for j = 1:cols % looping through columns
  
number = a(i, j);
  
prime = 1; % checking if number is prime
for one = 2:number-1
if mod(number, one) == 0
prime = 0;
break;
end
end
  
if prime == 1 % if so, adding it to sum
sum += number;
end
  
end
end

sum % printing sum

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