Find a position of last changing value in array

Hello,

i'm looking for function that detect a position of detection of last changing value (value stay constant or have just little changes).

In this case tube_dimension = 37;

I'm realize this in for-loop, but maybe thereare better way?

Sensivity_old = Sensivity;

TP ...
FN ....

Sensivity = (TP ./ (TP + FN));
if (Sensivity > Sensivity_old + 1.0e-03)
   Sencivity_end = tube_cnt;
else   
end

disp(Sencivity_end)

Thank you!

Answer 1

[Umair Hassan]

Hi Nikita,

You can use MATLAB's built in function differentrial (diff) to find out the minimum variability points of your data. The first index of the those points would be where your data would have the plateau. If you can attach some data, I would give you a code as well, otherwise psuedo code is:

plateau_points=diff(sensitivity);
plateau_points=find(plateau_points ==0) % finding where the points have 0 change
plateau_tube_dimension=tube_dimension(plateau_points(1));

Hope this helps,

Thanks!

[Nik Rocky]

Hi Hassan,

thanks for your response!

I trieded to do your Answer:

My input is:

Sensivity =

  Columns 1 through 18

    0.8749    0.8806    0.8860    0.9100    0.9114    0.9130    0.9361    0.9374    0.9480    0.9493    0.9539    0.9559    0.9576    0.9586    0.9596    0.9606    0.9609    0.9612

  Columns 19 through 36

    0.9619    0.9622    0.9626    0.9632    0.9639    0.9649    0.9659    0.9665    0.9672    0.9675    0.9675    0.9679    0.9682    0.9685    0.9685    0.9712    0.9728    0.9745

  Columns 37 through 50

    0.9768    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771    0.9771

after

    plateau_points=diff(Sensivity)

I get:

plateau_points =

  Columns 1 through 18

    0.0057    0.0054    0.0241    0.0013    0.0017    0.0231    0.0012    0.0106    0.0013    0.0046    0.0020    0.0017    0.0010    0.0010    0.0010    0.0003    0.0003    0.0007

  Columns 19 through 36

    0.0003    0.0003    0.0007    0.0007    0.0010    0.0010    0.0007    0.0007    0.0003         0    0.0003    0.0003    0.0003         0    0.0027    0.0017    0.0017    0.0023

  Columns 37 through 49

    0.0003         0         0         0         0         0         0         0         0         0         0         0         0

after:

plateau_points=diff(Sensivity);
plateau_points=find(plateau_points > 0); % finding where the points have 0 change
plateau_tube_dimension = nonzeros(plateau_points(end));

I get 37! Is a right one. Thank you very much!