# please, how can i make the plot on the x axis from 15 to 25 hertz to rest on the x axis. that is to make them start from zero. i have used detrend but, it is not working

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Matthew Worker on 9 Jul 2023
Edited: John Kelly on 2 Aug 2023
Hello can you help with the above question
Cris LaPierre on 18 Jul 2023
We are several steps removed from the original question. I suggest asking a new question in the forum.
Matthew Worker on 24 Jul 2023
some of the data i dropped are from an ongoing research, which i should not have dropped

Cris LaPierre on 10 Jul 2023
This is likely due to the resolution of your data. The signal is not able to capture everything, so over time, the error accumulates. There are likely techniques you can use when collecting the data to minimize this. However, since you already have the signal, I think you should try higher-order detrending. Here I picked 10 based solely on how the ouput looks
fs= 1000;
T=7;
dt= 1/fs;
tspan= (0:dt:T).';
yddot = acc;
ydot = cumtrapz(tspan,yddot);
ydot2 = detrend(ydot,10,"SamplePoints",tspan);
y = cumtrapz(tspan,ydot2);
plot(tspan,ydot2,tspan,y)
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Cris LaPierre on 10 Jul 2023
Edited: Cris LaPierre on 10 Jul 2023
Another approach might be to smooth your signal and then subtract the smoothed signal from the raw signal.
fs= 1000;
T=7;
dt= 1/fs;
tspan= (0:dt:T).';
yddot = acc;
ydot_raw = cumtrapz(tspan,yddot);
smoothedData = smoothdata(ydot_raw,"lowess","SmoothingFactor",0.125);
ydot = ydot_raw - smoothedData;
y = cumtrapz(tspan,ydot);
plot(tspan,ydot,tspan,y)
Cris LaPierre on 11 Jul 2023
Edited: John Kelly on 2 Aug 2023
Post that was deleted
Thank you very much for your response. what of the other question i asked? did you figured it out also?
______________________________________________________________________
Response
It seems you already have the code written for that, but you are only capturing the final result from your nested for loops.
You can capture it easily enough. You just need to make Energy a matrix instead of a vector.
Change
for c = 1.5:1:5.5
...
Energy(ii) = (trapz(tspan,c*(zdot).^2));
end
to something like
dcoeffs = 1.5:1:5.5;
for jj = 1:length(dcoeffs)
c = dcoeffs(jj);
...
Energy(ii,jj) = (trapz(tspan,c*(zdot).^2));
end

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