MATLAB: How to make a function that takes a matrix and integer and divide every divisible element of matrix by integer

Question

Hi everyone I am going to attempt that query: Write a function called divvy that takes a matrix A of positive integers and a single positive integer k as its two inputs and returns a matrix B that has the same size as A. The elements of B are all divisible by k. If an element of A is divisible by k, then the corresponding element in B must have the same value. If an element of A is not divisible by k, then the corresponding element of B must be the product of the given element of A and k. You are not allowed to use any for-­‐loops or while-­‐loops. For example, the call X = divvy([1 2 ; 3 4], 2) would make X equal to [2 2 ; 6 4]. I am using that codes

function B =divvy(A,k)
if rem(A,k)==0
 B=A;
else
    B=A(:,:)*k;
end
end

but getting that error..

Feedback: Your function made an error for argument(s) [1 4;5 2;6 0], 3
      Your solution is _not_ correct.

Any suggestion how can i correct my code? thanks in advance for assistance

Answer 1

There is no need to use slow find, when logical indexing is faster and neater:

function B = divvy(A, k)
B = A;
idx = rem(A,k)~=0;
B(idx) = k*A(idx);
end

And the test cases:

>> divvy([1,2;3,4], 2)
ans =
     2     2
     6     4
>> divvy([1,4;5,2;6,0], 3)
ans =
     3    12
    15     6
     6     0