Converting serial date numbers to datetime array

43 次查看（过去 30 天）

Peter Marienka 2019-4-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458690-converting-serial-date-numbers-to-datetime-array

评论： Peter Perkins 2019-5-3

Hello!

I'm sorry for bothering you all, but I'm really new to MatLab and trying to learn something new to help me with my research.

I've recently made som measurements and my outputs in txt shows time stamp in format "3718505030". I understood that this is MatLab Serial Data format, but I need to convert them into conventional data and time format. Probably the date is not included in this information. I've tried function

t = datetime(.3718505035,'ConvertFrom','datenum')

but it only converts to format HH:MM:SS, but I really need it in HH:MM:SS:SSS and also I need to apply the function on multiple rows.

Can you help me with this issue?

Thank you.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Stephen23 2019-4-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458690-converting-serial-date-numbers-to-datetime-array#answer_372407

编辑：Stephen23 2019-4-26

在 MATLAB Online 中打开

>> t = datetime(.3718505035,'ConvertFrom','datenum','Format','HH:mm:ss.SSS')
t =
   08:55:27.883

"also I need to apply the function on multiple rows"

>> V = [0.1;0.3;0.7];
>> t = datetime(V,'ConvertFrom','datenum','Format','HH:mm:ss.SSS')
t = 
   02:24:00.000
   07:12:00.000
   16:48:00.000

9 个评论
显示 7更早的评论隐藏 7更早的评论

Stephen23 2019-4-26

编辑：Stephen23 2019-4-26

"all numbers are shown as 3.7185e+09"

In your question you showed us that the data is "3718505030" and this should be interpreted as a decimal fraction, which you gave as datetime(.3718505035,..).

Now you have shown that that data is not a decimal fraction at all, but in fact has a magnitude 1e9. Quite different, so of course the ouputs are rubbish! Rubbish in -> rubbish out.

If the data should be interpreted as a decimal fraction of a day (e.g. as a serial date number), then you would need to convert it to a fraction first.

However it is quite possible that your data is actually a unix timestamp or some other encoding (rather than a MATLAB serial date number), in which case 3718505030 represents the date+time 2087-11-01T06:03:50 or whatever it encodes (if this is the case then pick the appropriate input option for datetime). Of course I cannot tell you what the date encoding is (they are just numbers), YOU need to know that based on the documentation of the data that you have. But until then, you can expect that rubbish in -> rubbish out.

Walter Roberson 2019-4-27

No, the user is treating the values as datenum and those are days since 1 jan 0 CE so using days() is appropriate

Peter Perkins 2019-5-3

Walter's right: if .3718505030 is supposed to be interpreted as "a little less than 9 hours," then using days to create a duration is the correct thing. That was one of the flaws of datenums: is it a long elapsed time, or an absolute date during the dark ages? The datetime/duration pair solves that problem.

I can't tell if it's days(.3718505030) or days(3718505030/1e10), but same difference.

请先登录，再进行评论。

请先登录，再回答此问题。

类别

MATLAB Language Fundamentals Data Types Time Series Time Series Objects

在 Help Center 和 File Exchange 中查找有关 Time Series Objects 的更多信息

产品

MATLAB

版本

R2019a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by