changing time step of data or resample the data
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I have a motion data with different time step as shown in figure. 1st column represent time step and 2nd to 4th column represent motion. Now, My problem is I want to change the time step of motion data in to uniform time step, say 0.02 sec. How can I change my time step to 0.02 sec time step in matlab? Any answer are highly appreciated. Thank you.
답변 (2개)
Jan
2016년 11월 10일
편집: Jan
2016년 11월 10일
Sort the rows at first to get an ascending order. Then call interp1:
xx = 0.001:0.02:1.0;
yy = interp1(x, y, xx)
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Guillaume
2016년 11월 11일
The problem is not with what it should be, it's not difficult to create that, the problem is with what it is now. Your input is not monotonous, so you need to decide what you want to do about it.
Guillaume
2016년 11월 10일
t = array2table(yourmatrix(:, 2:end), 'rowTimes', ...
datetime(0, 0, 0, 0, 0, yourmatrix(:, 1), 'Format', 'ss.SSS'));
The retime function has then plenty of options to resample your data over the interval and step you want, e.g.:
newtimes = datetime(0, 0, 0, 0, 0, 0) : duration(0, 0, 0.02) : datetime(0, 0, 0, 0, 0, 60);
newtimes.Format = 'ss.SS';
newt = retime(t, newtimes, 'linear');
However, the times in your original array need to be stricly monotonically increasing for any interpolation to work, so you will encounter the same issues as with Jan's answer.
The advantage of a timetable is that there are plenty of built-in function to resample values / aggregate them by period, etc.
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Guillaume
2016년 11월 11일
Well, you need to decide what you want to do about your input and these duplicated values. Matlab can't do that for you.
You can indeed only keep one set with unique (but which one, the duplicates are vastly different) but really you need to work out why you have duplicates in the first place and what it means. You could also aggregate the values (average / median / etc.), again only can decide what is appropriate
Once you've worked out what to do, then it is trivial to use interp1 or retime.
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