# Find the increasing and decreasing point in array?

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Sabarinathan Vadivelu on 20 Feb 2014
Commented: Image Analyst on 20 Feb 2014
I have an array. Which is increasing. At one point it starts decreases.
This trend starts repeating many times in array. How to find that point in array where the trend starts?
Image Analyst on 20 Feb 2014
Define "trend". Is it the start of the first increasing part of a signal where you have many rising/falling sections? Maybe you can post a screenshot of your data plotted and point out the element that you say the "trend" starts at.

Azzi Abdelmalek on 20 Feb 2014
Edited: Azzi Abdelmalek on 20 Feb 2014
A=[1 2 3 2 1 4 5 6 7 5 2 0 4 5 6 10]
[peaks,idx]=findpeaks(A)
If you haven't a signal processing toolbox
A=[5 2 3 2 1 4 5 6 7 5 2 0 4 5 6 10]
d=sign([0 diff(A)]);
idx=strfind(d,[1,-1])

Image Analyst on 20 Feb 2014
Use the diff() function
differences = diff(yourArray);
increasing values will be positive and decreasing values will be negative.