Convert a time string to double

Hi everyone,

I have a timestamp vector in seconds (in range 1.6573e+9 ) and converted it to datetime (I get for expl. 08-Jul-2022 09:42:56)

t = datetime(1970,1,1) + seconds(timeStamps) + hours(2); 

I'm not sure why I need to add 2 hours, but it works correctly. Now I want to search to see if the date I entered is included in timeStamps. Since my input date is a string and timeStamps is a double, I need to convert my date to double

ts = datenum( t - datetime(1970,1,1) - hours(2) ) ; 

I used the same converted vector t to test if I get the same values for timeStamps, but I get a wrong answer (in range 1.9181e+04)

So I wonder if someone can help me to solve this problem? Thank you

[Stephen23]

Don't use deprecated DATENUM, DATEVEC, or DATESTR.

Instead you should use the methods and functions that support DATETIME objects:

https://www.mathworks.com/help/matlab/date-and-time-operations.html

[Steven Lord]

I have a timestamp vector in seconds (in range 1.6573e+9 ) and converted it to datetime

Instead of manually creating the datetime representing January 1st, 1970 I'd suggest using the 'ConvertFrom' option for datetime with the 'posixtime' option.

...

Since my input date is a string and timeStamps is a double, I need to convert my date to double

No. Convert your string representing a date and time to a datetime array instead. Then use isbetween or relational operators (greater than, less than, etc.) on the datetime arrays.

Answer 1

[Star Strider]

I am not certain what you are doing, however the isbetween function (that does not require conversion out of datetime) may be what you want.

[Tasnim Sayadi]

After searching for the time I would like to read for example the Temperature, Humidity,... . Therefore I want to know not only if the date and time exists but also the index. isbetween returns only a logical value (true/false). Is there a way to get the index too?

[Star Strider]

The isbetween funciton returns a logical vector. Assuming your data are column-oriented, you would get all the rows with something like this —

Lv = isbetween(t, tupper, tupper); % Logical Vector

AllData = T{Lv,:}; % Return Matrix Of Relevant Data

where ‘t’ are the datetime data and ‘T’ is the table that contains it and the other data. (Note the use of curly brackets {} to return a matrix rather than a table.)

See the documentation I linked to earlier for more information.

.