# How to find the middle element of a square array

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Kevin Carty 2020 年 3 月 12 日

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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### 回答 (3 件)

Bhaskar R 2020 年 3 月 12 日

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
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Walter Roberson 2020 年 3 月 12 日
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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Piyush Lakhani 2020 年 3 月 12 日
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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Jada Roth 2020 年 9 月 10 日
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 = ceil(size(squareArray)/2);
% Assign middleElement with the center element of squareArray
middleElement = squareArray(elementIndex(1),elementIndex(2));
end

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