converting a table (having as first col a datetime col) col into a datetime (having both date & time in its composition)

Oftentimes a datetable has 2 adjacent columns: a datetime with a date and a string with a time. If one wants to concatenate these two into a datetime col having both date and time in it, one would be compelled to do:

Tab5Min = aImport5Min('myFile.txt');
Tab5Min.Date = datetime(strcat(datestr(Tab5Min.Date), " ", Tab5Min.Time),'InputFormat','dd-MMM-yyyy HH:mm');
Tab5Min.Time = [];
Tab5Min.Date = table2timetable(Tab5Min.Time ,"RowTimes","Date");

which is slow and unoptimal ... is there a better way?

further the the above ... subscripting by time ranges within a day within a resulting table as the above...

Say, one must substract all data samples between 01:00:00 and 02:30:00, one must do:

temp = Tab5Min;
temp.Date = timeofday(Tab5Min.Date);
S = timerange(duration('01:00:00','InputFormat','hh:mm:ss'),duration('02:30:00','InputFormat','hh:mm:ss'))
myResult = temp(S,:); 

It's just painful, especially compared to Pandas.

Ok, one might say - let's do 2 functions:

function tsTable = ConcatDateTimeCols(tsTable, inputFormat)
%
%   first 2 cols need to be named: Date (and to have datetime fields w/
%   dates), and Time (having strings of type: "hh:mm:ss" or "hh:mm"
%
    tsTable.Date = datetime(strcat(datestr(tsTable.Date), " ", tsTable.Time),'InputFormat',inputFormat);
    tsTable.Time = [];
    tsTable = table2timetable(tsTable, "RowTimes", "Date");    
end

function subScript = GetDayTimeRange(tsTable,startTime,endTime)
%
%   startTime & endTime need to be of format "18:45:00"
%
        
    tsTable.Date = timeofday(tsTable.Date);
    % if there are returns, compute them here;
    S = timerange(duration(startTime,'InputFormat','hh:mm:ss'), duration(endTime,'InputFormat','hh:mm:ss'));
    
    subScript = tsTable(S,:); 
    % if there are returns, compute cumsums here
end

but still is cumbersome ...

thanks

[Rik]

The faster way is to edit the parser function. Functions that do a lot of work for you tend to be slow, especially if you need to parse the output another time.

Answer 1

[Steven Lord]

Convert your text data into a duration array, specifying an 'InputFormat', and add the datetime and duration arrays together.

For your second section of code, store the duration array you created either in a separate variable or as a variable in your table or timetable then use logical indexing.

% Arbitrary data
n = 25;
dur = hours(randi([0 24], n, 1)) + minutes(randi([0 60], n, 1));

% Thresholds
start = duration(1, 30, 0);
stop = duration(6, 45, 0);

% Logical arrays
afterStart = start <= dur;
beforeStop = dur <= stop;
isInRange = afterStart & beforeStop;

% Display the data about which condition(s) the data satisfied
t = table(dur, afterStart, beforeStop, isInRange)

% Show which durations are between 1:30 AM (1 hour 30 minutes post midnight)
% and 6:45 AM
dur(isInRange)
% or
tooEarly = t(~afterStart, :)
tooLate = t(~beforeStop, :)
justRight = t(isInRange, :)