MATLAB: Calculate duration from cell with date hours with Matlab 2013a

datedurationr2013atime

I have a cell array of more than 16700 rows and 3 column as in the example below:

'01/01/2014'  '12:00:00'  'AM'
'01/01/2014'  '06:00:00'  'AM'
'01/01/2014'  '10:00:00'  'AM'
'01/01/2014'  '12:00:00'  'PM'
'09/04/2014'  '11:00:00'  'PM'

I would like to calculate the duration of two chosen dates and time (for example the last row-first raw=number of days, hours and seconds). My big problem is that I have a R2013a version of Matlab. So I can't use DateTime, I tried this:

newA = cellfun(@(s) strsplit(s, ' '), DateTime, 'UniformOutput', false); 
DateTimeSep = vertcat(newA{:});
%%Calculs de durée et récupération de données
date=datenum(DateTimeSep(:,1),'mm/dd/yyyy');
d=datestr(date(1256,1)-date(1,1), 'dd')
Time=DateTimeSep(10,2)-DateTimeSep(1,2)% I didn't try to consider the AM PM problem yet....

I get d=04 (which is false) and for time I get: "Undefined function 'minus' for input arguments of type 'cell'"

Best Answer

% [Don't use this - see [EDITED 2] for a nicer solution!]
D = {'01/01/2014'  '12:00:00'  'AM'; ...
     '01/01/2014'  '06:00:00'  'AM'; ...
     '01/01/2014'  '10:00:00'  'AM'; ...
     '01/01/2014'  '12:00:00'  'PM'; ...
     '09/04/2014'  '11:00:00'  'PM'};
DateV = datevec(strcat(D(:, 1), '#', D(:, 2)), 'mm/dd/yyyy#HH:MM:SS');
IsPM  = strcmpi(D(:, 3), 'PM');
pstPM = (DateV(:, 4) < 12 & IsPM);
DateV(pstPM, 4) = DateV(pstPM, 4) + 12;  % 12:01PM ==> 12:01, 1:01PM ==> 13:01
midAM = (DateV(:, 4) == 12 & ~IsPM);
DateV(midAM, 4) = 0;                     % 12:01AM ==> 00:01
DateN = datenum(DateV);

Now the time difference can be calculated by a simple subtraction.

datevec(DateN(end) - DateN(1))  % [EDITED, DateTimeN -> DateN]

[EDITED 2] No, the conversion of the time difference to months and years is not meaningful: It is not clear if the "month" has 28, 29, 30 or 31 days, if it concerns the difference between dates. Better:

Duration     = DateN(end) - DateN(1);
DurationDays = fix(Duration);
Tmp          = rem(Duration, 1);  % Time
DurationHour = floor(Tmp * 24);
DurationMin  = floor(rem(Tmp *  1440, 60));
DurationSec  = round(rem(Tmp * 86400, 60));

Sorry, this is too ugly! Nicer:

D = {'02/14/2014', '10:02:04', 'AM'; ...
     '02/26/2014', '01:00:00', 'PM'};
DateN = datenum(strcat(D(:, 1), '#', D(:, 2), '#', D(:, 3)), ...
                'mm/dd/yyyy#HH:MM:SS#AM');
Duration = DateN(end) - DateN(1);
DDays    = fix(Duration);
[~,~,~, Dhour, Dmin, Dsec] = datevec(rem(Duration, 1));

Related Solutions

MATLAB: Timezone to UTC: How to add duration vector to datetime vector

Frank, what's up is Daylight Saving Time, which occurred on March 8th this year. I'm guessing you knew that, but got mixed up in the time arithmetic. Here's what's going on. You have this:

>> time = ['2015/03/08 00:00';'2015/03/08 01:00';'2015/03/08 03:00';'2015/03/08 04:00'];
>> Time = datenum(time,'yyyy/mm/dd HH:MM')
Time =
                    736031
          736031.041666667
                736031.125
          736031.166666667

datenums don't know anything about time zones or DST. Those times mean whatever you want them to mean. Since you then do this ...

>> date = datetime(Time,'ConvertFrom','datenum','Timezone','America/Montreal')
date = 
   08-Mar-2015 00:00:00
   08-Mar-2015 01:00:00
   08-Mar-2015 03:00:00
   08-Mar-2015 04:00:00

... I assume you mean that those datenums are to be interpreted as times in the America/Montreal time zone. But what you've left out is this:

>> date.Format = [date.Format ' z']
date = 
   08-Mar-2015 00:00:00 UTC-5
   08-Mar-2015 01:00:00 UTC-5
   08-Mar-2015 03:00:00 UTC-4
   08-Mar-2015 04:00:00 UTC-4

The second and third times are only an hour apart. Then this ...

>> [UTC_Offset,dst] = tzoffset(date);
>> Date = date - UTC_Offset
Date = 
   08-Mar-2015 06:00:00 UTC-4
   08-Mar-2015 07:00:00 UTC-4
   08-Mar-2015 07:00:00 UTC-4
   08-Mar-2015 08:00:00 UTC-4

... adds 5 hours to the first and second times, but adds only 4 hours to the third and fourth times. But you're doing the addition in the America/Montreal time zone. Adding 5 hours to the first two puts them after the DST shift @2am, which makes them look like you added 6 hours. In other words, your array is not UTC, it's shifted America/Montreal. The easiest thing to do to get UTC times is this:

>> date.TimeZone = 'UTC'
date = 
   08-Mar-2015 05:00:00 UTC
   08-Mar-2015 06:00:00 UTC
   08-Mar-2015 07:00:00 UTC
   08-Mar-2015 08:00:00 UTC

Hope this helps.

MATLAB: Can’t convert a cell array to a date using cellfun(@datenum or @datetime)

You do not need to use cellfun to convert your cell array to datetime, but you do need to specify the format of your input string, and since you've got a timezone specified, which timezone you want the datetime in:

c = {'2012-03-12 00:00:00 UTC'
'2010-09-06 00:00:00 UTC'
'2010-10-24 00:00:00 UTC'
'2010-09-06 00:00:00 UTC'
'2012-02-06 00:00:00 UTC'
'2010-09-06 00:00:00 UTC'
'2012-05-22 00:00:00 UTC'
'2011-09-23 00:00:00 UTC'
'2011-06-21 00:00:00 UTC'
'2012-05-30 00:00:00 UTC'
'2012-05-31 00:00:00 UTC'
'2010-10-15 00:00:00 UTC'};
d = datetime(c, 'InputFormat', 'yyyy-MM-dd HH:mm:ss z', 'TimeZone', 'UTC')

The same using cellfun (which as stated is completely unnecessary):

d = cellfun(@(s) datetime(s, 'InputFormat', 'yyyy-MM-dd HH:mm:ss z', 'TimeZone', 'UTC'), c, 'UniformOutput', false);
d = vertcat(d{:})

Best Answer

Related Solutions

MATLAB: Timezone to UTC: How to add duration vector to datetime vector

MATLAB: Can’t convert a cell array to a date using cellfun(@datenum or @datetime)

Related Question