I have some data that was given to me in excel and the time format is rather confusing. The fist column of the is the DateTime but with incorrect HH:MM and the second column is the correct hour of the day HH:MM:
time = {'01/01/2000 00:00',num2str(2300);
'01/01/2000 00:00',num2str(2400);
'01/01/2000 00:00',num2str(10);
'01/01/2000 00:00',num2str(100)};
However, when the time exceeds midnight, instead of being 00:10 the time is 10, and 01:00 is 100. How could I alter these to the correct format? i.e. from the example above I would like the outcome to be:
time = {'01/01/2000 23:00';
'01/01/2000 24:00';
'01/01/2000 00:10';
'01/01/2000 01:00'};
How could I achieve this?
Using sprintf in MATLAB, you can use the field width specifier:
where
Field width:
Minimum number of characters to print. Can be a number, or an asterisk (*) to refer to an argument in the input list. For example, the input list ('%12d', intmax) is equivalent to ('%*d', 12, intmax).
Thus your times should end up all looking like "XX:XX", with the leading zero added by the sprintf if it is missing and the colon added in.
Thanks to #Junuxx for the exact command: sprintf('%02i:%02i', hours, minutes)
To separate hours and minutes, you would obviously do time % 100 to get the minutes and integer divide by 100 to get the hours.
From there, you simply strcat or concatenate ["a" "b"] your two columns to get your desired result.
Related
I have data (240 x 9 dimensions) in which a DATETIME column has entries as shown below. I want to separate the date and time parts. Also, I need to calculate the time difference between an entry and a previous one. The date is formatted as yyyymmdd followed by the hhmmsssss. However, the last three entries of the seconds represent the decimal seconds i.e., 36200 means 36.2 seconds
Using MATLAB I have separated the date and time entries as character arrays as the original data was in the double format as below:
datestr: 240 x8 char e.g., '20190101'
timestr: 240 x9 char e.g., '001634200'
I want to convert the date into the standard format. I used
formatOut = 'yyyy/mm/dd';
date=datestr(datenum('20190101','yyyymmdd',1900),formatOut);
But getting this error : Index in position 1 exceeds array bounds (must not exceed 240).
Additionally, I need to convert the time into hh:mm:ss.sss format and then calculate the difference between a time and its previous entry.
Any help will be appreciated.
I have the following values in Excel:
Bed time 19:34:00
Get up time 07:04:00
Time in bed 11:30:00
Sleep start 19:42:00
Sleep end 07:00:00
I want to import them into MATLAB and do some calculation on these time values such as subtraction. The time values look like this after importing:
0.8153
0.2944
0.4792
0.8208
0.2917
and obviously doing calculation on them would be nonsense. Would any body help me with this issue? I have stuck with it for few days, and no progress yet.
Thanks in advance,
As assylias pointed out, these are fractions of days. You can use the datestr function to convert it to human-readable strings with formatting option conveniently.
e.g.:
datestr(0.2917, 'HH:MM:SS')
ans =
07:00:02
Calculations such as subtractions can be done on the raw values before
conversion.
E.g: get duration of sleep.
start = 0.8208
stop = 0.2917
datestr(stop-start, 'HH:MM')
ans =
11:18
Even works for intervals that span over midnight.
I am trying to read time-coordinate data from a netCDF file using matlab. I have a netCDF file (which I created) that has a time variable in the format of a double corresponding to the number of hours from a specific time (see below).
Variable attributes:
double time(Time) ;
time:standard_name = "Time" ;
time:units = "hours since 2002-01-01 0:0:0" ;
time:calendar = "proleptic_gregorian" ;
When I read the time variable using ncread) into matlab, it just prints out an integer e.g.,1. However, if I use "ncdump" to explore the file, I see the time variable in it's coordinate time e.g., 2002-01-01 01.
Specifically: "ncdump -t -v time ncfile.nc"
I'm relatively new to matlab, and I was wondering if anyone knew if there was a similar, or an equally simple, way to read this time variable as its coordinate time into matlab, either as a string, or numerical date. Specifically, I would like to avoid having to parse the attribute string and code up a bunch of pointers and conditions to convert the integer data to an actual date.
Alternatively, should I just create a new time variable in these files that is just an array of dates as strings?
Any information is very much appreciated!
Thanks!
NetCDF stores time as an offset from an epoch. From your variable attribute, your epoch is 2002-01-01 0:0:0, and the time is hours since then. Matlab has a similar methodology called date numbers, although it is based off of days since an epoch (which they call pivot years). There are two functions that you should look into: datenum and datestr. The first converts a string into a date number and the other converts a date number into a date string.
You can convert your time variable into a compatible Matlab date number by dividing by 24 and then use the datestr function to format it however you like. Here is a simple example:
>> time = [1;2;3;4];
>> datestr(time./24+datenum('2002-01-01 0:0:0'))
ans =
01-Jan-2002 01:00:00
01-Jan-2002 02:00:00
01-Jan-2002 03:00:00
01-Jan-2002 04:00:00
Look at the Matlab help files associated with the two functions and you can format the date output however you like.
Is it possible to concatenate multiple variable horizontally to make a single variable in Matlab?
For Example, I want to join:
year = 2001, month = 06, day = 15
to make one variable '20010615' which I could search in a matrix.
I hope I am clear.
Regards,
If you want a string output, use string formatting and sprintf
sprintf('%04d%02d%02d', year, month, day );
If you want a numeric output, simply multiply
day + 100 * month + 10000 * year
Update:
Thanks to #Joshua's comment: if you are indeed working with date/time information you should also look into datestr that allows more speciallized formatting for date and time information.
How can I convert this kind of data 08:00:43.771 given as string into a number specifying the number of milliseconds since midnight corresponding to this time instance?
I generally use the Matlab datenum outputs for timestamping in Matlab. Datenums are the number of days since 0/0/0000, expressed as a double (double precision numbers are precise to about 14 usec for contemporary dates).
Using datenums.
currentDateTime1 = datenum('08:00:43.771'); %Assumes today
currentDateTime2 = datenum('6/8/1975 08:00:43.771'); %Using an explicit date
millisecondsSinceMidnight = mod(currentDateTime1 ,1) *24*60*60*1000; %Mod 1 removes any day component
millisecondsSinceMidnight = mod(currentDateTime2 ,1) *24*60*60*1000; %Then this is just a unit conversion
For unusual string formats, use the extended form of datenum, which can accept a string format specifier.
Use 1000*etime(datevec('08:00:43.771'),datevec('0:00')) to give the number of milliseconds since midnight. etime gives the number of seconds between two date vectors, datevec converts strings to date vectors (assuming Jan 1 this year if only a time is given).