Converting Date and Time to Number

Hi guys,

I have read in a column of dates and times from an excel document using xlsread and now have a cell of dates in the form 'yyyy-mm-dd hh:mm:ss AM/PM'.

I would like to extract from this cell a vector with the time in the form hhmm. How might I go about doing this?

Thanks,

Justin

Answer 1

[Star Strider]

See datenum, datestr and their friends.

[Justin Duval]

Thanks for the quick answer. I have successfully used datestr to put the date and time data into the form dd-mm-yyyy hh:ss:mm as a char element.

I am now having difficulty using datenum to get me any further. My data is in 15 minute increments where the time is more important than the date. Is there a way that I can now extract just the time from my char element in the form hhmm so that I may use it in my code going forward?

[Star Strider]

You simply have to remember that upper-case letters indicate time fields and lower-case letters date fields.

Example:

dt = {'2014-02-10 10:15:27 PM'};                % Original Date
dn = datenum(dt, 'yyyy-mm-dd HH:MM:SS AM');     % Date Number
ts = datestr(dn, 'HHMM')                        % Desired Time Format

produces:

ts =

2215

You also have to specify 'AM' or 'PM' (it doesn’t matter which) in the appropriate field if you have times designated as such. MATLAB will do the conversion automatically. (Here it converted 10 PM correctly as 22 in the ‘ts’ assignment.

[Justin Duval]

YES! That worked great, and you're right, my problem was forgetting that I needed to use upper-case letters to indicate time fields.

Thanks very much for your help.

Justin

[Justin Duval]

Of course I've come across another obstacle. I now have my time data in the HHMM form I need it in, but as a char. Is it possible to convert this vector of char data into a vector of numerical data?

EDIT: Scratch that. I converted the character array to a cell array using cellstr, and converted that to a numerical vector using str2double.

IF there is a smarter way to do this, please let me know. Thanks again for your help!

Justin

[Star Strider]

My pleasure!

If you want the date fields as numeric, use the datevec function:

dt = {'2014-02-10 10:15:27 PM'};                % Original Date
dn = datenum(dt, 'yyyy-mm-dd HH:MM:SS AM');     % Date Number
tv = datevec(dn);                               % Date Vector
hhmm = tv(:,4:5)                                % Get Hour & Minute Fields

produces:

hhmm =

      22    15