convert array string data in array serial number

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Luca Re
Luca Re 2023-5-23
评论： Luca Re 2023-5-23
this example clarify my problem
>> size(B)
ans =
463628 1
>> B(1)
ans =
"01/01/2008"
>> datenum(B(1,:),'dd/mm/yyyy')
ans =
733408
>> datenum(B,'dd/mm/yyyy')
Error using datenum
DATENUM failed.
Caused by:
Error using dtstr2dtnummx
Failed to convert from text to date number.
i can convert the single string but not the array of strings
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Stephen23
Stephen23 2023-5-23
编辑：Stephen23 2023-5-23
Ran in:
"What do you recommend if I have empty array elements?"
Use DATETIME instead of deprecated DATENUM:
B = ["01/01/2008";""]
B = 2×1 string array
"01/01/2008" ""
D = datetime(B, "InputFormat","dd/MM/yyyy")
D = 2×1 datetime array
01-Jan-2008 NaT
Luca Re
Luca Re 2023-5-23
yes but i want do preallocate it
is it correct to do it like this? (i need 5600 element in this matrix and I have to assign values ​​read from .txt
dataan=NaT(righe,colum);

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回答（1 个）

Steven Lord
Steven Lord 2023-5-23
Ran in:
Unless you're using an older release where it is not available I strongly recommend you use datetime instead of serial date numbers. Note I've changed your B slightly to make it clear that datetime is importing it correctly, not confusing the day and month information.
B = "02/03/2008";
dt = datetime(B, "InputFormat", "dd/MM/yyyy")
dt = datetime
02-Mar-2008
With a datetime array a lot of operations are easier and easier to interpret than with a list of date numbers. As an example, what's the day after dt?
nextDay = dt + days(1)
nextDay = datetime
03-Mar-2008
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Stephen23
Stephen23 2023-5-23
编辑：Stephen23 2023-5-23
Ran in:
"i've problem to use it"
It will work when you read and follow the DATETIME documentation or the example that Steve Lord showed you. Why did you change the syntax to something completely different?
S = "01/01/2008";
D = datetime(S, 'InputFormat','dd/MM/yyyy')
D = datetime
01-Jan-2008

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