How to count elements in array until criteria is met and output number of elements?

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Nicholas Kavouris 2022-3-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1682544-how-to-count-elements-in-array-until-criteria-is-met-and-output-number-of-elements

评论： Matt J 2022-3-29

I have an array documenting states of a system and need to find system active duration.

An array looks something like

[1 1 1 1 2 2 2 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 1 1 1 2 2 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5]

Each integer is the system state output from the controller. How can I create a method to count the number of elements in the array until the array becomes 5 (shutdown), repeat counting for the next system cycle, and output the duration (number of elements) of each cycle independently?

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Answer 1

Image Analyst 2022-3-28

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https://ww2.mathworks.cn/matlabcentral/answers/1682544-how-to-count-elements-in-array-until-criteria-is-met-and-output-number-of-elements#answer_928774

在 MATLAB Online 中打开

Try using regionprops(), if you have the Image Processing Toolbox (type ver to check)

v = [1 1 1 1 2 2 2 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 1 1 1 2 2 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5];
v5 = v == 5;
% Find starting locations and durations
props = regionprops(v5, 'PixelList', 'Area');
for k = 1 : length(props)
	startingLocations(k) = props(k).PixelList(1,1);
end
startingLocations % Echo to command window
startingLocations = 1×2
    33    58
durations = [props.Area] % How many 5's are in each run of 5's.
durations = 1×2
     4     3