plz give me a solution

Question

Darshan Kanungo 2015-5-30

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评论： grooshka 2018-4-16

Write a function called large_elements that takes as input an array named X that is a matrix or a vector. The function identifies those elements of X that are greater than the sum of their two indexes. For example, if the element X(2,3) is 6, then that element would be identified because 6 is greater than 2 + 3. The output of the function gives the indexes of such elements found in row-‐ major order. It is a matrix with exactly two columns. The first column contains the row indexes, while the second column contains the corresponding column indexes. For example, the statement indexes = large_elements([1 4; 5 2; 6 0], will make indexes equal to [1 2; 2 1; 3 1]. If no such element exists, the function returns an empty array.

function found = large_elements(A)
[row col] = size(A);
found = [];
for ii = 1:row
for jj = 1:col
if A(ii,jj) > ii + jj
found = [found; ii jj];
else found = [];
end
end
end
end

Problem 4 (large_elements): Feedback: Your function performed correctly for argument(s) 1

    Feedback: Your function performed correctly for argument(s) [1 2 3 4 5 6 7 8 9 10]
    Feedback: Your function made an error for argument(s) [10 9 8 7 6 5 4 3 2 1]
    Your solution is _not_ correct.

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Walter Roberson 2017-7-5

Jyoti, that is what I suggested two years ago.

grooshka 2018-4-16

What is the purpose of n variable?

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Answer 1

Walter Roberson 2015-5-30

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In the "else" case, leave found unchanged instead of overwriting all of it with [].

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Edward Kofi Mahama 2017-11-11

Please why did you add " n=0" and "n = n+1" to the code. I don't understand why the code should not work without that. Can you please help explain? Thanks in advance

Walter Roberson 2017-11-11

在 MATLAB Online 中打开

Jyoti Sharma added the counter. I do not know why.

There is another way of writing the code that does use a counter:

function y = small_elements(v)
[r,c] = size(v);
n=0;
y = [];
for j = 1:c
  for i = 1:r
      if v(i,j) < i*j;
          n = n+1;
          y(n,:) = [i j];            
      end
    end
end

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Answer 2

Jorge Alberto Fuentes Casillas 2017-4-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/221456-plz-give-me-a-solution#answer_263408

编辑：Walter Roberson 2017-4-18

在 MATLAB Online 中打开

This code is for this case: "Write a function called small_elements that takes as input an array named X that is a matrix or a vector...."

function indexes = small_elements(v) 
[i j] = size(v);
position = 0;
indexes_rows = []; 
indexes_columns = [];
if ~isempty(v) 
    for columns = 1:j 
        for rows = 1:i 
            elem_in_i = v(rows,columns); 
            product_ij = rows*columns;
              if elem_in_i<product_ij
                  position = position+1;
                  indexes_rows(position) = (rows);
                  indexes_columns(position) = (columns);
              end 
          end 
      end 
      if isempty(indexes_rows) || isempty(indexes_columns)
          indexes = [];
      else
          indexes = [indexes_rows',indexes_columns']; % A matrix of only 2 columns is created.
      end 
else 
    indexes = [];
end
end