Is there a way to detect a drop in values in an array?

Hello, I would like to know if there is a way to detect a sudden drop in values in an array. Matlab should see when a gap starts and tell me in which class it happens. How do I get Matlab to recognize the large gap which starts in class 16 (see picture).

Here is the reason: My program should be able to recognize two piles of points. Therefore I have computed all distances from each point to an fixed vector (in each slice/plane). Afterwords I have classed them by distance. The gap in the classes means, that there is also a big gap between the points. Thus a new pile of points begins. Thank you.

Answer 1

[Image Analyst]

You can threshold to find all elements less than a certain number:

lowAmounts = amount < 10; % Logical vector - use find() if you want actual indexes.

Or you can use findpeaks() in the signal Processing Toolbox to find valleys in your data

[peakValues, locations] = findpeaks(-amount);

Or you can use the diff() function to find big changes from one element to the next

differences = diff(amount);
bigDrops = differences < -15; % or whatever value you want.

They're slightly different, so it just depends on what you want exactly.

[Leo Müller]

Thank you, I will try it out!

[Image Analyst]

Actually I forgot to invert the amounts in findpeaks. I corrected it, and the correct line is:

[invertedPeakValues, locations] = findpeaks(-amount);