Can you temporarily remove a column from timetable?

I have a time table and want to remove a column that marks true or false, so it can be retimed (retime does not work if there are characters), then add it back once retime is finished.

[Walter Roberson]

Suppose you retime events at times 1.07 and 2.18 and 4.6 to times 1, 2, 3, 4. Then how do you know what value of the flag to associate with each of the new entries?

[ZH]

I have timestamps that are meausred every second for a few hours so I would like to average the retime then go from there.

[dpb]

Turn the variable to categorical() and then set the 'VariableContinuity' property to match the data type.

However, you also can apply different methods by specifying the VariableContinuity property of the timetable. You can specify whether each variable contains continuous or discrete data. Then the retime function applies a different method to each timetable variable, depending on the corresponding VariableContinuity value.

If you specify VariableContinuity, then the retime function fills in the output timetable variables using the following methods:

• 'unset' — Fill in values using the missing data indicator for that type (such as NaN for numeric variables).
• 'continuous' — Fill in values using linear interpolation.
• 'step' — Fill in values using previous value.
• 'event' — Fill in values using the missing data indicator for that type.

[ZH]

[filename, pathname] = uigetfile('*.csv'); %opens dialog box to grab file
T = readtable(strcat(pathname,filename)); 
TT=table2timetable(T); 
 
origvars = TT.Properties.VariableNames; 
newvars = regexprep(origvars, '_', ''); 
has_unit = contains(origvars, '_Units'); 
TT.Properties.VariableNames = newvars ; 
TT(:,has_unit ) = [];
TT.Properties.VariableContinuity(contains(TT.Properties.VariableNames,'TestFlag'))={'continuous'};
TT_new2 = retime(TT,'minutely', 'mean'); 

[ZH]

Does something look off to you?

[Walter Roberson]

It would help to have the first few lines of the table TT

[ZH]

Attached is table TT

[dpb]

Unfortunately, there's a caveat I didn't include on using 'VariableContinuity'

"If you do specify a method as an input argument to retime or synchronize, then that method overrides the values you specify inVariableContinuity."

[Walter Roberson]

In your sample data, every non-numeric column other than the timesamp, had the same content for the entire column. Does that hold true for the entire file? For example is TestFlag false for the entire file?

[ZH]

No it does not hold true. I shortened it for the upload, so once data hits a specific number, the TestFlag turns true.

[Steven Lord]

So it's like the example I posted, only instead of going from true to false your data goes from false to true?

[ZH]

Correct

[Walter Roberson]

Suppose the entry at 6.8 has the flag false, and the entry at 7.2 has the flag true, then when retime tries to create the entry for 7.0 should the flag be set to false or to true or to round(interp1([6.8 7.2], [0 1], 7.0)) ?

Answer 1

[Steven Lord]

Selecting only variables of a certain type is easy if you index into the timetable using a vartype. Adding the variables that you didn't retime back into the timetable is likely to be trickier.

dt = datetime('now')+minutes([0; 5]);
T = timetable(dt, [0; 5], [true; false])
V = vartype('double');
R = retime(T(:, V), 'minutely', 'linear')

What should be the values for Var2 in each row of R? If it should be a logical variable, where should the transition from true to false take place? If it should be a double variable, why not just cast it to double in T using double before calling retime?