Extract a portion of an accelerometric signal around a maximum

Hello to everyone, I have an accelerometric signal (1st column : time ; 2nd column : acceleration values);

I would like to find the y_max and the corresponding x_max (I am able to do it) and starting from that precise point, extract a portion of the signal, for example 5 seconds before and 5 seconds after that point. I would like to write this new portion of the signal in a new file. This is how I started the code:

clc;
close all;
clear all;

format long

T = readtable('AT4H1X11.ASC','filetype','text','decimal',',');
T(:,3:end) = [];


Fsa=600;                %frequenza di acquisizione
Ta=1/Fsa;               % periodo di acquisizione

t_acc=T.Var1;           %estrapolazione prima colonna (tempi);
s_acc=T.Var2;           %estrapolazione seconda colonna (accelerazioni);


%N_s_acc=length(s_acc);                      % Numeno di valori 
%t_s_acc=linspace(0,N_s_acc*Ta,N_s_acc);     % Ricostruzione tempi

AT4H1X11_max_acc=max(abs(s_acc(1:end,1)))

T_arr=table2array(T);

[ymax,idy]=max(abs(T_arr(:,2)))
xmax=T_arr(idy,1)

Thank you very much!

[dpb]

Fsa=600;                %frequenza di acquisizione
Ta=1/Fsa;

so, how many samples at 600 Hz is 5 sec? Select that many elements +/- of your max index you've already found...

Or, if you convert the table to timetable instead of array (and you don't need to do that to do what you've done anyway, just reference the table variables instead), then the time column will be in duration format and you can select by comparison of time values instead of computing indices.

Or, the timeseries object for this could be another convenient way...

[Guglielmo Giambartolomei]

Thank you dpb but I find difficult to transform your idea in a code.

[dpb]

So what have you tried and where did you get stuck?

[Guglielmo Giambartolomei]

I think I'm able to select the points I need but then? How can I really extract that portion? Thank you!

[dpb]

With any computed indexing expression using x(n1:n2) if compute the indices directly; if you use the time series objects, there are methods to return the values that satisfy isbetween() or again indexing with logical expressions relative to the time value...

So, show us what you've tried so far...attaching a sample data file often entices folks to actually look at the real case 'cuz it's something interesting! :)

[Amrtanshu Raj]

Hi,

Can you attach the 'AT4H1X11.ASC' file so that we can understand your problem and help you with the exact solution for your case.

[Guglielmo Giambartolomei]

Hi Amrtanshu,

unfortunately the ASCII file is bigger than 5 mb.

Thank you anyway!