MATLAB Answers

Adding rows to matrix conditionally

조회 수: 1(최근 30일)
HOl
HOl 31 Mar 2020
댓글: HOl 1 Apr 2020
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

  댓글 수: 1

Star Strider
Star Strider 31 Mar 2020
I will defer to Guillaume’s Answer, since he posted the solution first. The data file is attached.

댓글을 달려면 로그인하십시오.

채택된 답변

Guillaume
Guillaume 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

  댓글 수: 6

표시 이전 댓글 수: 3
HOl
HOl 1 Apr 2020
The version I have is 2019b (trial version).
I had noticed that this time column was super wacky, but the data is the output of a software that unfortunately does not let me change anything in how it exports.
I tried the algo you recommend and it goes through without error (victory!) and the output is ALMOST what I need. The number of rows is correct and the states have been repeated correctly.
The but is that the time column, now "dateTimeUnified" does have 30 s increments but does not start at the same time as the original time.
In the original data the start time in first row was "21:18:52" so I need the "new time" go:
newtime = 21:18:52
21:19:22
21:19:52
21:20:22, etc
Is it possible to make the "DateTimeUnified" start from the first time stamp?
Guillaume
Guillaume 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');
HOl
HOl 1 Apr 2020
Excellent, that works. Thank you very much!!
For any other newby's out there with wonky data here is the final code:
>> opts = detectImportOptions('data.csv'); %have to use import options because of the wonky format of the file
>> opts = opts.setvartype(3, 'char');
>> data = readtable('data.csv', opts); %import as table
>> data.(3) = duration(strrep(data.(3), ' PM', '')); %get rid of the useless PM, then convert to duration
>> data.DateTimeUnified = data.(2) + data.(3) + seconds(data.(4) / 1e6); %convert microseconds to seconds and add the whole lot
>> data.DateTimeUnified.Format = 'dd MMM yyyy HH:mm:ss.SSSSSS';
>> data(end, :) = []; %get rid of the last row which is nonsense
>> tdata = table2timetable(data, 'RowTimes', 'DateTimeUnified'); %convert to timetable
>> newtimes = (tdata.DateTimeUnified(1):seconds(30):tdata.DateTimeUnified(end)+seconds(30))';
>> resampled = retime(tdata, newtimes, 'previous');

댓글을 달려면 로그인하십시오.

추가 답변(1개)

Andrei Bobrov
Andrei Bobrov 31 Mar 2020
out = [(x(1,1):x(end,1))',repelem(x(:,2),[diff(x(:,1));1])];

  댓글 수: 0

댓글을 달려면 로그인하십시오.

태그

제품

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by