How to select a sub square matrix, from a matrix; given the size of the sub square matrix and middle element

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MANOGNA POTLURI 2020-8-9

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评论： MANOGNA POTLURI 2020-8-9

M = [
  10    16    15    66    76
  28    98    43     4    75
  55    96    92    85    40
  96    49    80    94    66
  97    81    96    68    18 ]

i need sub sqaure matrices, given size ofthe sub matrix and middle element.

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Walter Roberson 2020-8-9

You did not really answer the question though. Is the requirement to locate the center of the matrix according to a given value? Or would you instead be given a position ?

MANOGNA POTLURI 2020-8-9

I'm sorry I didn't get the question first time;

yes, I have the value of the middle element, and I have to find it in the matrix and use that as the centre of the submatrix to extract

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Walter Roberson 2020-8-9

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编辑：Walter Roberson 2020-8-9

use find() with two output arguments to get the row and column of the center. Then use indexing like row-something:row+something

You need to make some decisions about how to handle the case of a matrix size that is even. For example if you are asked to return a 2 x 2 matrix relative to the value 4, then how would you resolve that?

You also need to make decisions about the case where the value is found close to an edge of the matrix, and decisions about the case where the value is found multiple times. Also decisions about the case where a larger array is asked for than the size of the original matrix.