Can't assign VariableUnits to TimeTable

I'm trying to create a timetable for a motor simulation. I would like to keep track of the units of each variable.

Here is my code, a script in a file called CreateTT.m:

time.start = duration(0,0,0,0); %Start: 0m, 0s, 0ms
time.end = duration(0,1,0,0);   %end: 1m
time.step = duration(0,0,0,1);  %step: 1 ms

time.numsteps = (time.end - time.start) / time.step;

varNames = {'Angle','Angular Speed','Voltage','Current','Magnetic Field'};
varTypes = {'double','double','double','double','double'};
varUnits = {'degrees','deg/s','Volts','Amps','Tesla'};

data = timetable('Size', [time.numsteps, 5], 'VariableTypes', varTypes, 'TimeStep', time.step, 'VariableNames', varNames, 'VariableUnits', varUnits);

Error using timetable
Invalid parameter name: VariableUnits.

When I run it, I get the following error:

Error using timetable (line 335)

Invalid parameter name: VariableUnits.

Error in CreateTT (line 11)

data = timetable('Size', [time.numsteps, 5], 'VariableTypes', varTypes, 'TimeStep', time.step, 'VariableNames', varNames, 'VariableUnits', varUnits);

I am using R2021a, Update 7. As you can see above, I ran the code using the "Run" button here in the forum and got the same error.

I checked the online documentation for making a timetable and 'VariableUnits' is definitely a valid parameter to use. When I omit that part, my code runs fine, and if I check data.Properties, it shows 'VariableUnits' as one of the properties (albeit blank, of course).

What am I doing wrong?

Answer 1

[Star Strider]

For some reason, it doesn’t like 'VariableUnits' as part of the initial timetable declaration.

This alternative approach works —

time.start = duration(0,0,0,0); %Start: 0m, 0s, 0ms
time.end = duration(0,1,0,0);   %end: 1m
time.step = duration(0,0,0,1);  %step: 1 ms

time.numsteps = (time.end - time.start) / time.step;
varNames = {'Angle','Angular Speed','Voltage','Current','Magnetic Field'};
varTypes = {'double','double','double','double','double'};
varUnits = {'degrees','deg/s','Volts','Amps','Tesla'};
data = timetable('Size', [time.numsteps, 5], 'VariableTypes', varTypes, 'TimeStep', time.step, 'VariableNames', varNames);
data.Properties.VariableUnits = varUnits;

Check = data.Properties.VariableUnits

Check = 1×5 cell array
    {'degrees'}    {'deg/s'}    {'Volts'}    {'Amps'}    {'Tesla'}

.

[Captain Karnage]

Star - thank you for the workaround. After posting, I looked at timetable.m, and it appears that 'VariableUnits' (and a few others) is missing from the cell array used to check the name / value pairs, despite being mentioned as valid in the comments in multiple places. I think this is a bug.

[Star Strider]

It very well might be a bug. I had similar problems creating a table recently, although with a different name-value pair. I used the same approach as with your problem.

That aside, the workaround seems to produce the desired result.