MATLAB Answers

How to find the middle element of a square array

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Kevin Carty
Kevin Carty on 12 Mar 2020
Commented: Walter Roberson on 12 Mar 2020
function middleElement = FindMiddle(squareArray)
% FindMiddle: Return the element in the center of squareArray
% Inputs: squareArray - n x n input array, where n is odd
%
% Outputs: selectedData - center element of squareArray
% Assign elementIndex with location of middle row/col
% Hint: Use the size() function to deterimine the dimension of squareArray
elementIndex = size(squareArray)
% Assign middleElement with the center element of squareArray
middleElement = squareArray(elementIndex)
end
How do I start this? I figure I would have to set the elementIndex to an integer but I don't know how to do that. Any guidance would be appreciated.

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Answers (2)

Piyush Lakhani
Piyush Lakhani on 12 Mar 2020
Hi Kevin,
The 'size' function returns the two element array 'row and column'. As what i can understand you want a single value that determines the variable 'n'.
so may be 'length' function gives the output you wants. Try in following way.
function middleElement = FindMiddle(squareArray)
% FindMiddle: Return the element in the center of squareArray
% Inputs: squareArray - n x n input array, where n is odd
%
% Outputs: selectedData - center element of squareArray
% Assign elementIndex with location of middle row/col
% Hint: Use the size() function to deterimine the dimension of squareArray
elementIndex = length(squareArray)
% Assign middleElement with the center element of squareArray
middleElement = squareArray(elementIndex)
end

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Bhaskar R
Bhaskar R on 12 Mar 2020
Edited: Bhaskar R on 12 Mar 2020
function middleElement = FindMiddle(squareArray)
% FindMiddle: Return the element in the center of squareArray
% Inputs: squareArray - n x n input array, where n is odd
%
% Outputs: selectedData - center element of squareArray
% Assign elementIndex with location of middle row/col
% Hint: Use the size() function to deterimine the dimension of squareArray
center_ind = (size(squareArray)+1)/2;
% Assign middleElement with the center element of squareArray
middleElement = squareArray(center_ind(1), center_ind(2))
end

  2 Comments

Kevin Carty
Kevin Carty on 12 Mar 2020
Can you explain why you did +1 to the size?
Walter Roberson
Walter Roberson on 12 Mar 2020
N is odd. If you divide it by 2 you will get a leftover 1/2, but you cannot use 1/2 as an index.
Example: n=7. 7/2=3.5 but you cannot use 3.5 as an index. What is the proper index?
1234567
!
The ! has the same number of elements before and after so the index of the center is 4.
Now take (7+1)/2 and you get 4 which is the correct index. This can also be thought of as 7/2 + 1/2 = 3.5+.5 = 4: just group the operation differently, 7/2+1/2 times 2 is 7 + 1, so divide by the 2 is (7+1)/2

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