Create new table wit differentiate or diff from existing timetable
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I've got below timetable with daily measurements from my gas meter at home:
Timestamps GasM3
____________________ _____________
14-Aug-2019 00:00:00 331.15
25-Aug-2019 00:00:00 332.37
26-Aug-2019 00:00:00 332.74
27-Aug-2019 00:00:00 333.97
I would like to know the daily consumption, so I tried playing with "differentiate" & "diff" to get these values in a new table.
I've tried
Test1 = differentiate(DailyGasDataTimeTable)
which gave the following error:
Error using Visualization: Differential test</a> (line 17</a>)
'differentiate' requires Curve Fitting Toolbox
and
Test2 = diff(DailyGasDataTimeTable)
which gave the following error:
Undefined function 'diff' for input arguments of type 'table'.
Error in Visualization: Differential test (line 17)
Unfortunately I'm stuck, please advise.
Kind regards,
Daniel
0 Comments
Answers (4)
Vinod
on 28 Aug 2019
Edited: Vinod
on 28 Aug 2019
You can extract the specific column, GasM3, from the timetable and use the diff function. Something like this:
data = thingSpeakRead(YourChannelNum,'OutputFormat','TimeTable');
deltaM3 = diff(data.GasM3);
newTable = timetable(data.Timestamps(2:end), deltaM3)
2 Comments
Kristina Collins
on 31 Aug 2020
What if my timetable is missing entries, or the entries are unevenly timed?
Olavo
on 21 Aug 2023
Edited: Walter Roberson
on 21 Aug 2023
Hello, Thanks for your answer it's very helpful!
What if I the variable I what to differentiate is not a fixed name and will be changing along the code? for example:
for i=1:10;
deltaM(i) = diff(data.GasM3{i}); % -->> does not work with this notation
end
3 Comments
Steven Lord
on 21 Aug 2023
Or you could use a numeric index.
T = array2table(magic(4))
A = T{:, 3} % Equivalent to T.Var3
If you're release R2023a or later, you may be able to compute directly on the table or timetable, as described on this documentation page.
T2 = diff(T)
Olavo
on 22 Aug 2023
Thanks Walter and Steven, very useful information.
Just to add some extra information, I found the function wildcardPattern very useful to get similar names from table. would be something like:
varname = "GasM3" + wildcardPattern;
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