Not able to convert string to seconds! Even though I am using datenum function. How can it be solved?

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John 2023-7-30

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评论： Walter Roberson 2023-7-30

I have been trying to convert time string from a large datal, but it Matlab gives me "Unrecognized millisecond format. Format string: HH:MM:SS.FFFF."

And I would like to get the data immediately from the file instead of importing them.

The format of the string is

12:10:02.908990

Here is the code:

t1;

datenum(t1,'HH:MM:SS.FFFF')

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Answer 1

masoud sistaninejad 2023-7-30

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在 MATLAB Online 中打开

in MATLAB R202a and later you can use

datetime command like this ...

t1 = '12:10:02.908990'
t1 = '12:10:02.908990'
datetime(t1)
ans = datetime
   30-Jul-2023 12:10:02

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Answer 2

Walter Roberson 2023-7-30

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编辑：Walter Roberson 2023-7-30

在 MATLAB Online 中打开

datenum() only supports up to millisecond resolution -- so at most FFF .

Also, your input format needs to account for the entire input string. You cannot just specify FFF and expect it to stop parsing after it reads 3 digits of milliseconds.

t1 = '12:10:02.908990';
d = duration(t1, 'InputFormat', 'hh:mm:ss.SSSSSS', 'format','hh:mm:ss.SSSSSS')
d = duration
   12:10:02.908990
datenum_you_were_looking_for = seconds(d) / (24 * 60 * 60)
datenum_you_were_looking_for = 0.5070
ds = datestr(datenum_you_were_looking_for, 31)  %cross-checking
ds = '0000-01-00 12:10:02'

I don't think the number of days since the beginning of "0 AD" is going to be useful, especially with the lost resolution (because datenum just do not have the resolution)- You should probably be seriously considering getting rid of using datenum()

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Stephen23 2023-7-30

编辑：Stephen23 2023-7-30

"What are other alternatives to datenum()? "

Lets read the DATENUM documentation and see what it tells us:

The DURATION class would suit your input data (times given as hours, minutes, seconds + fraction of second). Note the DURATION class has properties and methods that you will find useful.