how to make a function that takes a matrix and integer and divide every divisible element of matrix by integer

Question

Muhammad Usman Saleem 2015-5-28

0
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https://ww2.mathworks.cn/matlabcentral/answers/219968-how-to-make-a-function-that-takes-a-matrix-and-integer-and-divide-every-divisible-element-of-matrix

回答： charu sharma 2015-8-20

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

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Stephen23 2015-5-28

编辑：Stephen23 2015-5-28

@Muhammad Usman Saleem: Your code concept is fundamentally flawed, because by using an if statement the allocation and multiplication operations are mutually exclusive, whereas they actually need to be able to operate on the same matrix. Using if does not help you! See my answer to know how this can be done.

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Answer 1

Stephen23 2015-5-28

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https://ww2.mathworks.cn/matlabcentral/answers/219968-how-to-make-a-function-that-takes-a-matrix-and-integer-and-divide-every-divisible-element-of-matrix#answer_180763

编辑：Stephen23 2015-5-28

在 MATLAB Online 中打开

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

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Stephen23 2015-5-28

编辑：Stephen23 2015-5-28

在 MATLAB Online 中打开

function B = divvy(A, k)
% Allocate the output matrix:
B = A;
% Indices of A that are not multiples of k:
idx = rem(A,k)~=0;
% Multiply those element values by k:
B(idx) = k*A(idx);
end