Adding rows to matrix conditionally
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I have long datafiles that I need to alter and cannot figure out how to do this.
The simplified version of what I'm trying to do is:
x = 1 20
3 50
6 10
Column 1 is time (t) (sec 1, 3, 6) and col 2 the values.
I want to create a new matrix with time axis with 1 sec interval and that the values (col 2) are repeated until next (t) ( in col1)
The resulting matrix should be:
x2 = 1 20
2 20
3 50
4 50
5 50
6 10
Sorry about the elementery question, I'm a newby
1 Comment
Star Strider
on 31 Mar 2020
I will defer to Guillaume’s Answer, since he posted the solution first. The data file is attached.
Accepted Answer
Guillaume
on 31 Mar 2020
We don't have enough details to give you a complete answer but what you want to do should be easily done by
- reading your file as a timetable. Could be as easy as:
data = readtimetable(yourfile);
depending on the actual file
- retime the timetable to 1 second interval, which is simply:
resampled = retime(data, 'secondly', 'previous'); %retime in one second interval using the previously known value for the missing times
- save into a new file
writetimetable(resampled, 'newfile.csv');
for example
6 Comments
Guillaume
on 1 Apr 2020
You can construct a new time vector starting at the time of your choosing and pass that to retime instead of letting it construct it:
newtimes = (tdata.DateTimeUnified(1):seconds(30):tdata.DateTimeUnified(end)+seconds(30))';
resampled = retime(tdata, newtimes, 'previous');
More Answers (1)
Andrei Bobrov
on 31 Mar 2020
out = [(x(1,1):x(end,1))',repelem(x(:,2),[diff(x(:,1));1])];
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