how to find the distance at which the change rate of values increases or decreases abruptly?

1 view (last 30 days)

Hailong on 13 Nov 2013

0
Link

Direct link to this question

https://www.mathworks.com/matlabcentral/answers/105911-how-to-find-the-distance-at-which-the-change-rate-of-values-increases-or-decreases-abruptly

Closed: MATLAB Answer Bot on 20 Aug 2021

Hi all, I have some electrical resistance data across a tree trunk (see the attached data file, in which the first three pairs of columns are the coordinates and the last column is the resistance). Since the resistance of sapwood (SW) and heartwood (HW) should be different to a large degree, I want to identify the SW-HW boundary from plotting of the data or simple transformation of the data (to find the abrupt change, perhaps the derivative using diff? I'm not sure).

Can anyone show me how to achieve it automatically instead of visual identification? Expected result: the distance at which the biggest change happens.

ps: by distance, I mean the value in the coordinates (actually the coordinates are the depth from the bark of tree), for example in the following picture, the distance from 0 point in x-axis.