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Unable to detect datetime or duration data using readtimetable with a seconds index

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Bill Tubbs
Bill Tubbs on 13 Apr 2021
Commented: Bill Tubbs on 13 Apr 2021
Here is a toy example of my problem:
% Create a timetable with a seconds index
data = timetable(seconds(1:3)', randn(3,1), randn(3,1))
writetimetable(data, "test.csv")
data_in = readtimetable("test.csv")
Output:
data =
3×2 timetable
Time Var1 Var2
_____ ________ _________
1 sec -0.10224 0.31286
2 sec -0.24145 -0.86488
3 sec 0.31921 -0.030051
Error using readtimetable (line 190)
Unable to detect datetime or duration data in file '/Users/username/test.csv' for row times.
The content of the CSV is as follows:
Time,Var1,Var2
1 sec,-0.225584402271252,0.0325574641649735
2 sec,1.11735613881447,0.552527021112224
3 sec,-1.08906429505224,1.10061021788087
For comparison, this works fine:
% Create a timetable with a regular datetime index
dt = datetime({'2015-12-18 08:00:00';'2015-12-18 08:01:00';'2015-12-18 08:02:00'});
data = timetable(dt, randn(3,1), randn(3,1));
writetimetable(data, "test.csv")
data_in = readtimetable("test.csv")

Accepted Answer

Cris LaPierre
Cris LaPierre on 13 Apr 2021
Edited: Cris LaPierre on 13 Apr 2021
The issue appears to be that seconds get written in a format that MATLAB cannot read back in. The only supported input formats for durations are
  • 'dd:hh:mm:ss'
  • 'hh:mm:ss'
  • 'mm:ss'
  • 'hh:mm'
  • Any of the first three formats, with up to nine S characters to indicate fractional second digits, such as 'hh:mm:ss.SSSS'
The values are written with the units: 1 sec
For now, I would recommend creating and saving the timetable using one of the recognized formats.
% Create a timetable with a seconds index
data = timetable(duration(zeros(3,1),zeros(3,1),(1:3)'), randn(3,1), randn(3,1))
data = 3×2 timetable
Time Var1 Var2 ________ ________ ________ 00:00:01 -0.35574 0.35245 00:00:02 -0.60954 -0.22619 00:00:03 0.6993 1.9414
writetimetable(data, "test.csv");
data_in = readtimetable("test.csv")
data_in = 3×2 timetable
Time Var1 Var2 ________ ________ ________ 00:00:01 -0.35574 0.35245 00:00:02 -0.60954 -0.22619 00:00:03 0.6993 1.9414
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