How do I compare a current discrete value of a signal with a previous discrete value?
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Hi, How do I compare the current discrete value with a previous discrete value? It would be nice to see a simple matlab coded example, if possible. Is there a way to do that in simulink? Thanks!
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Ameer Hamza
le 27 Mai 2018
Here is an example
x = [1 4 2 6 2 4];
y = diff(x)
y =
3 -2 4 -4 2
diff() will subtract every value with the previous value. If the value given by diff() is greater then 0, then it means that the current value is larger than the previous value, similarly, a negative value means current value is smaller then previous.
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Image Analyst
le 27 Mai 2018
To compare elements of a signal with the elements immediately prior to them use diff(), as Ameer showed. To compare a whole signal to a later whole signal, then you'll have to save your original signal so it can be subtracted later:
oldSignal = signal; % Save a copy of the current signal.
% Now the signal changes somehow... Now check the difference:
differenceSignal = signal - oldSignal;
That's assuming that the "comparison" you want to do is a simple subtraction and not something else, like exclusive OR or spectral change or whatever.
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kat001
le 27 Mai 2018
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Image Analyst
le 27 Mai 2018
Yes, I gave you an idea. The code I gave will work for that case. Basically save your current value as the "old" value, then when you get a new value in subtract the old value from it and redefine the old value as the current value.
TAB
le 27 Mai 2018
Modifié(e) : TAB
le 27 Mai 2018
In Simulink you can use Unit delay block to extract previous step value and Relational Operator to compare.
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