Converting dates into numbers

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Sergio
Sergio 2013-9-10
回答： Peter Perkins 2018-9-12
I have a int32 matrix of dates in the format YYYYMMDD and a cell array for time in the day in the format HH:MM. How can I combine both and turn it into a number I can use for plotting?

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Azzi Abdelmalek
Azzi Abdelmalek 2013-9-10
x=int32([19921212,19921213,19921214])'
y={'12:12', '13:13','14:14'}'
a=[num2str(x) char(y)]
b=datenum(a,'yyyymmddHH:MM')
datestr(b)
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Silver
Silver 2018-9-11
@Azzi and when I have the date format already sticked together like this: 2016.03.01 14:38:00 in a cell array how can I convert them to numeric so I can ue them in plot ? thks in advance
Stephen23
Stephen23 2018-9-11
@Silver: read the datenum documentation.

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Peter Perkins
Peter Perkins 2018-9-12
Unless you're using a fairly old version of MATLAB, consider using datetimes instead of datenums. You will be happier.
>> x = int32([19921212,19921213,19921214])';
>> y = {'12:12', '13:13','14:14'}';
>> d = datetime(x,'ConvertFrom','yyyymmdd')
d =
3×1 datetime array
12-Dec-1992 00:00:00
13-Dec-1992 00:00:00
14-Dec-1992 00:00:00
>> t = duration(y,'InputFormat','hh:mm')
t =
3×1 duration array
12:12:00
13:13:00
14:14:00
>> dt = d + t
dt =
3×1 datetime array
12-Dec-1992 12:12:00
13-Dec-1992 13:13:00
14-Dec-1992 14:14:00
Then just plot whatever vs. dt. You don't need to convert the datetimes to numeric.
Actually, creating the duration directly form text requires R2018a, prior to that do this:
>> t = timeofday(datetime(y,'InputFormat','HH:mm'))
t =
3×1 duration array
12:12:00
13:13:00
14:14:00
or use text2duration on the File Exchange.

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