Did I do anything wrong when I used the "second" function?

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원석 서
원석 서 2022-2-4
编辑： Stephen23 2022-2-4
I have the date data.
I'm using a program created by a previous person.
However, the following problems arise.
CurrentTime = datenum("2022-02-04 15:23:26");
INPUTDATA.SS = second(CurrentTime);
Check for incorrect argument data type or missing argument in call to function 'second'.
I have to keep using this, but I want to know what's wrong.
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Stephen23
Stephen23 2022-2-4
编辑：Stephen23 2022-2-4
Ran in:
@KSSV: simply showing the first result is not sufficient to determine which overloaded function will be called for a specific input class, for that you need to use the -all flag:
which second -all
/MATLAB/toolbox/finance/calendar/second.m /MATLAB/toolbox/matlab/datatypes/datetime/@datetime/datetime.m % Shadowed datetime method /MATLAB/toolbox/matlab/bigdata/@tall/second.m % Shadowed tall method /MATLAB/toolbox/parallel/parallel/@codistributed/second.m % Shadowed codistributed method
Then we can clearly see that the remaining functions are really methods of specific classes (not double). If the user does not have the financial toolbox then none of the remaining class methods accept a DOUBLE input.

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Stephen23
Stephen23 2022-2-4
编辑：Stephen23 2022-2-4
Ran in:
"Did I do anything wrong when I used the "second" function?"
Yes, you supplied the wrong input class: as its documentation clearly states the function SECOND is only defined for DATETIME objects. It will not work with serial date numbers (which are double class), which is what you tried.
You should use a DATETIME object and avoid deprecated DATENUM:
T = datetime("2022-02-04 15:23:26")
T = datetime
04-Feb-2022 15:23:26
S = second(T)
S = 26
Do not mix up the functions:
  • SECOND (which only works with DATETIME objects, but is part of MATLAB)
  • SECOND (which is part of the the Financial Toolbox, and you probably do not have)
  • SECONDS (which will accept a DOUBLE input and return a DURATION object, but give a meaningless output if you try it with a serial date number)
  • any other function you might have on your path named SECOND...
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Stephen23
Stephen23 2022-2-4
编辑：Stephen23 2022-2-4
@KSSV: you showed in your earlier comment that you are using the Financial Toolbox function SECOND:
https://www.mathworks.com/help/finance/second.html
which does accept a serial date number input argument. But clearly the OP does not have this, although the person who originally wrote the code may have had. I would not presume, as you do, that a user has all toolboxes installed.
That confusion is one of the disadvantages of MATLAB's lack of proper packages.

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