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Index for array max (or min) in Simulink without variable-size signal or MATLAB Function block

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In Simulink I have a signal that is a 1-D array. I need to get the index associated with the first maximum (or minimum) value in the array. In MATLAB, that's simply this:
>> [val,idx] = max([2 3 6 8 4 7 8 4 5 6])
val =
8
idx =
4
where idx is the item I'm looking for.
Trying to do that in Simulink seems to be much less straightforward. The MinMax block does not offer an option to output the index of the first maximum value.
Coupling a MinMax with a Find Nonzero Elements blocks as in the suggestion on this page does do the trick, but it comes with the problem that the output of the find block is a variable-sized signal. I don't want it to be a variable sized signal; I just want the first index.
One could also use a MATLAB Function block and use the MATLAB min or max function as above, but MATLAB Function blocks take obnoxiously long to compile and often generate code with a lot of gunky overhead.
Is there not a simple, clean, cheap way to get the first max index?
  1 Commento
Michael
Michael il 3 Ott 2017
FYI to anyone who stumbles across this page...MathWorks staff saw this question and generated an enhancement request for the MinMax block on 2 OCT 2017. Even if that eventually gets added to base Simulink, it doesn't help me in the near term at all.

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Risposta accettata

Peter Anderson
Peter Anderson il 26 Apr 2018
I was looking at this sort of problem (for me it was find the first non-zero element) and came up with a solution that doesn't involve toolboxes, MATLAB function blocks or variable size signals. You can solve it with a for-iterator subsystem.
Your min/max case will be slightly different but will have very similar structure.
  3 Commenti
Juan Ocampo
Juan Ocampo il 4 Dic 2018
Congratulations great solution, thank you very muck for shearing it, i was thinking for a solution to this problem for a while and your solution is perfect.

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Più risposte (4)

sl
sl il 13 Feb 2019
Hi Michael,
The logic below will fulfill your need.
Capture.PNG

Marco
Marco il 3 Ott 2017
Hello Michael, you can try to use Maximum and Minimum block (DSP System Toolbox).
BR Marco
  1 Commento
Michael
Michael il 3 Ott 2017
Those blocks do look like they'll do the job. Unfortunately I don't have the DSP System Toolbox so it's not really a viable solution for me. It seems incredible that you can't get the capability I'm looking for without an inefficient workaround like a MATALB Function block or buying an extra toolbox, but that seems to be the case...

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Kirankumar Bacchewar
Kirankumar Bacchewar il 15 Ott 2021
Modificato: Kirankumar Bacchewar il 15 Ott 2021
This model can be used to find min,max and its Index. Just modify the size of the input array in selector blocks. Hope its helpful.

Mohammad Ali Sadeghian
Mohammad Ali Sadeghian il 27 Apr 2023
Hello,
you can use 2-D Maximum block with value and index.
ALI

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