Finding upper and lower (min and max) states

I have signals which contaiin multiple pulses which somewhat vary from each other. I am calculating the upper(max) and lower(min) states of each pulse in order to calculate rise and fall time for each indivisual pulse. As i have only the basic matlab with me ,i cannot make use of the functions risetime, statelevels which would calculate the required accurately , so proceeding mathematically.

[darova]

Can you show something?

[SHANTANU KSHIRSAGAR]

yes i have figure of some data related to signal

Answer 1

[Star Strider]

The 'movmedian' method works as well as 'sgolay', and appears to produce essentially the same result. It is a core MATLAB function introduced in R2016a. You should have it.

There is nothing in the documentation that says the 'sgolay' method requires the Signal Processing Toolbox, so I assumed it was implemented independently.

T = readtable('data.xlsx');
T.Var3 = smoothdata(T.Var2, 'movmedian', 3000);
[Lc,m,b] = ischange(T.Var3, 'linear', 'Threshold',5);
Cix = find(Lc);
Ic = [Cix m(Cix) b(Cix) T.Var1(Cix,:) T.Var2(Cix,:)];                       % Consolidation Matrix
risetime = Ic(2:4:end,4) - Ic(1:4:end,4);
falltime = Ic(4:4:end,4) - Ic(3:4:end,4);
statelo = Ic(1:4:end,5); 
statehi = Ic(3:4:end,5);

figure
plot(T.Var1, T.Var2)
hold on
plot(T.Var1, T.Var3, '-r')
plot(T.Var1(Cix), T.Var3(Cix), 'pg', 'MarkerFaceColor','g')
hold off
grid
legend('Original Data', 'Smoothed Data', 'Change Points', 'Location','E')

The smoothing method is all that is changed here. Experiment with the window length in the smoothdata call (3000 in my code) to get different results. (I am using R2020a.)

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[SHANTANU KSHIRSAGAR]

can we not do the replica of the commands used in pulse transition characteristics. as in the second image sent to find out states .when the previous code is used or even the derivative approch is used the start and end of rise and fall are approximately calculated. but in rise time command it is calculated almost accurately. can the same be done mathematically or the algorithm(one by one steps) for finding the rise time fall time be known.

[Star Strider]

If you have access to the Signal Processing Toolbox functions that produced the information in ‘untitled.2.jpg’ why not just use that? I thought you wrote that you did not have access to the Signal Processing Toolbox functions (such as risetime, falltime, and statelevels, one of which produced that plot).

If you have acces to those functions, why waste time with all the rest of this? I am not going to attempt to reproduce all that with my code, since my code is intended to be an approximation of that information, in the absence of the Signal Processing Toolbox.

The ‘untitled.2.jpg’ does not appear use the code I most recently posted. My code produced this plot with the data you posted:

My code is reasonably robust, although as I mentioned, it might be necessary to change (probably increase) the window length in the smoothdata call for different data sets. It will be necessary to experiment with that.

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[SHANTANU KSHIRSAGAR]

Yes I do not have the toolboxes on the system at my workplace. Currently I am working from home on my indivisual system so I could send you the another result. Really appritate your code , it is robust, I will work on it to get the results. Thank you .

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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