error using etime (datevec)

I have a csv file with times for experiment start and end. I'm trying to use etime to work out the time difference but im getting the following error. Can anybody help?

fid = fopen('time.csv');
out = textscan(fid,'%s %f %f %s','delimiter',',','headerlines',1);
fclose(fid);
com = out{1};
com2 = out{2};
com3 = out{3};
start_t = out{4};
dt2 = start_t(1);
gap_sec = etime(datevec(dt2),datevec(dt1));
time = gap_sec + time;

Error using datevec (line 225)
Failed to lookup month of year.

Answer 1

[Star Strider]

If R2014b or later is available, try this —

T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/896495/time.csv')

T1 = 2×3 table
                                Var1                                     Var2             Var3     
    _____________________________________________________________    ____________    ______________

    {'START,0.000000000000000E0,1.644373511592961E9,"2022-02-08'}    20:25:11.593    {'UTC-06:00"'}
    {'PAUSE,1.800001135500000E4,1.644391511601876E9,"2022-02-09'}    01:25:11.602    {'UTC-06:00"'}

C = regexp(T1{:,1}, '\d*\.\d*E\d', 'match');
n = cell2mat(cellfun(@(x)str2double(x), C, 'Unif',0));
Dates = datetime(n(:,2), 'ConvertFrom','Posixtime');
ElapsedTime = diff(Dates);
ElapsedTime.Format = 'hh:mm:ss.SSS'

ElapsedTime = duration
   05:00:00.008

The initial regexp call returns the POSIX numbers as strings. The ‘n’ and ‘Dates’ assignments extract the numerical data from the strings and convert them to datetime arrays. Using the diff funciton (to get the elapsed time) automatically returns the result as a duration array (here a scalar) and the last line sets the display 'Format' to show the milliseconds as well.

.

Answer 2

[Seth Furman]

We can import the table using import options to specify the delimiter and datetime format.

See also the following documentation pages.

detectImportOptions, setvaropts, readtable, datetime

fname = "https://www.mathworks.com/matlabcentral/answers/uploaded_files/896495/time.csv";
opts = detectImportOptions(fname,"Delimiter",",","TextType","string","VariableNamingRule","preserve")

opts = 
  DelimitedTextImportOptions with properties:

   Format Properties:
                    Delimiter: {','}
                   Whitespace: '\b\t '
                   LineEnding: {'\n'  '\r'  '\r\n'}
                 CommentStyle: {}
    ConsecutiveDelimitersRule: 'split'
        LeadingDelimitersRule: 'keep'
       TrailingDelimitersRule: 'ignore'
                EmptyLineRule: 'skip'
                     Encoding: 'UTF-8'

   Replacement Properties:
                  MissingRule: 'fill'
              ImportErrorRule: 'fill'
             ExtraColumnsRule: 'addvars'

   Variable Import Properties: Set types by name using setvartype
                VariableNames: {'event', 'experiment time', 'system time' ... and 1 more}
                VariableTypes: {'string', 'double', 'double' ... and 1 more}
        SelectedVariableNames: {'event', 'experiment time', 'system time' ... and 1 more}
              VariableOptions: Show all 4 VariableOptions 
	Access VariableOptions sub-properties using setvaropts/getvaropts
           VariableNamingRule: 'preserve'

   Location Properties:
                    DataLines: [2 Inf]
            VariableNamesLine: 1
               RowNamesColumn: 0
            VariableUnitsLine: 0
     VariableDescriptionsLine: 0 
	To display a preview of the table, use preview

opts.VariableTypes{4} = 'datetime';
inputFormat = "uuuu-MM-dd HH:mm:ss.SSS ZZZZ";
opts = setvaropts(opts,4,"InputFormat",inputFormat,"TimeZone","UTC");
t = readtable(fname,opts)

t = 2×4 table
     event     experiment time    system time         system time text      
    _______    _______________    ___________    ___________________________

    "START"             0         1.6444e+09     2022-02-09 02:25:11.593 UTC
    "PAUSE"         18000         1.6444e+09     2022-02-09 07:25:11.602 UTC

diff(t{:,4})

ans = duration
   05:00:00