Use conditions on a matrix and manipulate the results
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Hello,
I have a matrix:
a = [1 1 1 1; 0.99 1 1 1; 0.98 0.99 1 1; 0.97 0.99 0.99 0.99]
I would like to obtain the following result:
b = [0 0 0 0; 2 0 0 0; 0 3 0 0; 0 0 4 4]
It means that at the first time when 1 changes to 0.99 look up which row is it and write it in the 'b' matrix at the same place. If this condition is not true, write zero.
Thank you!
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Accepted Answer
Star Strider
on 29 Sep 2014
This works:
a = [1 1 1 1; 0.99 1 1 1; 0.98 0.99 1 1; 0.97 0.99 0.99 0.99];
q1 = a(1:end-1,:) - a(2:end,:); % Subtract Rows From Offset Rows
q2 = a(2:end,:)==0.99; % Find Offset Rows = 0.99
q3 = [zeros(1,size(a,2)); q1 & q2]; % Create Logical Matrix (Cond 1 & Cond 2)
b = bsxfun(@times, q3, [1:size(a,1)]'); % Use ‘bsxfun’ To Number The Row Entries
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