Problem 647. Getting the absolute index from a matrix

Created by Doug Hull

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This is a basic MATLAB operation. It is for instructional purposes.---You may already know how to get the <a href="http://www.mathworks.com/matlabcentral/cody/problems/646-getting-the-row-and-column-location-from-a-matrix">row and column index from a matrix</a>, and the <a href="http://www.mathworks.com/matlabcentral/cody/problems/640-do-a-binary-comparison-on-a-vector">logical indexing</a> technique but there is another way to reference specific elements in a matrix.Absolute indexing refers to specific elements with a single scalar rather than two (row and column). The upper left entry is value 1, the lower right is the highest value. MATLAB is column major, so you count down the rows in a specific column first, moving right as needed until you reach the end.<a href="http://www.mathworks.com/matlabcentral/cody/problems/645-getting-the-indices-from-a-vector">Indexing into a vector</a> is really using this kind of indexing, but it is more natural feeling.Use <a href="http://www.mathworks.com/help/techdoc/ref/find.html">Find</a>.Given a matrix M, return the absolute indices where M is greater than scalar, LB (Lower Bound) and less than UB (Upper Bound). (See <a href="http://www.mathworks.com/matlabcentral/cody/problems/640-do-a-binary-comparison-on-a-vector">Binary comparison</a> to satisfy two conditions)

This is a basic MATLAB operation. It is for instructional purposes.

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You may already know how to get the <http://www.mathworks.com/matlabcentral/cody/problems/646-getting-the-row-and-column-location-from-a-matrix row and column index from a matrix>, and the <http://www.mathworks.com/matlabcentral/cody/problems/640-do-a-binary-comparison-on-a-vector logical indexing> technique but there is another way to reference specific elements in a matrix.

Absolute indexing refers to specific elements with a single scalar rather than two (row and column).  The upper left entry is value 1, the lower right is the highest value.  MATLAB is column major, so you count down the rows in a specific column first, moving right as needed until you reach the end.

<http://www.mathworks.com/matlabcentral/cody/problems/645-getting-the-indices-from-a-vector Indexing into a vector> is really using this kind of indexing, but it is more natural feeling.

Use <http://www.mathworks.com/help/techdoc/ref/find.html Find>.

Given a matrix M, return the absolute indices where M is greater than scalar, LB (Lower Bound) and less than UB (Upper Bound). (See <http://www.mathworks.com/matlabcentral/cody/problems/640-do-a-binary-comparison-on-a-vector Binary comparison> to satisfy two conditions)

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Last Solution submitted on May 15, 2021

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1 Comment

Informaton on 29 May 2017

The test suite gives an answer.

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