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

3 views (last 30 days)
Nicholas Kavouris on 28 Mar 2022
Commented: Matt J on 29 Mar 2022
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?

Image Analyst on 28 Mar 2022
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
Nicholas Kavouris on 28 Mar 2022
i do not, appreciate the help though
Image Analyst on 28 Mar 2022
Well that gets you the number of non-5 counts though.
By the way, take a look at splitapply(), groupsummary(), and findgroups(). They are handy functions to know about.

Matt J on 28 Mar 2022
Edited: Matt J on 28 Mar 2022
Then,
array = [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];
G=groupTrue(array~=5);
[~,~,durations]=groupLims(G,1)
durations =
32 21
Nicholas Kavouris on 29 Mar 2022
Can this function be used for multiple conditons? Also reading your examples does not include the groupLims fcn
Matt J on 29 Mar 2022
Can this function be used for multiple conditons?
You mean like this?
G=groupTrue(array~=5 & array~=2);
The argument to groupTrue can be any logical vector.
Now you have one!

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