Date Conversion

2011 12 19
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0 个投票

Hi,
I have a <200x1 cell> array which consists of dates read through a text file. The dates are in the format yyyy/mm/dd hh:mm:ss:fff. I want to convert these dates into a matlab recognizable date vector which could then be later used in creating time series objects. I am not sure how to do this.
Thanks,

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Jan
Jan 2011-12-19
Are you sure about the colon before the fractional seconds? Usually there is a dot.
Syed Abbas
Syed Abbas 2011-12-19
Oh, that works now! I mistook the colun for the dot. Thansk a lot for ponting that out.

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Fangjun Jiang
Fangjun Jiang 2011-12-19

0 个投票

datenum()
>> dates={'2011/11/11 11:11:11:111';'2012/12/12 12:12:12:121'}
datenum(dates,'yyyy/mm/dd HH:MM:SS:FFF')
dates =
'2011/11/11 11:11:11:111'
'2012/12/12 12:12:12:121'
ans =
1.0e+005 *
7.3482
7.3522

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Syed Abbas
Syed Abbas 2011-12-19
I get the following error when I use datenum():
Error using datenum (line 181)
DATENUM failed.
Caused by:
Error using dtstr2dtnummx
Failed on converting date string to date number.
datenum() works if I have a single date but I have a date variable of type [200 x 1 cell] and want to convert all the dates in this variable at once
Jan
Jan 2011-12-19
Please post the inputs you are using.
Syed Abbas
Syed Abbas 2011-12-19
I keep getting the same error I meantioned earlier
Jan
Jan 2011-12-19
For which input? Please post an exact copy.
Fangjun Jiang
Fangjun Jiang 2011-12-19
Copy the exact command in the answer. You see it worked fine on my computer.
Syed Abbas
Syed Abbas 2011-12-19
Thats how my imputs look like:
'2011/12/15 09:00:00.039'
'2011/12/15 09:00:00.039'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.321'
'2011/12/15 09:00:00.323'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.333'
'2011/12/15 09:00:00.353'
'2011/12/15 09:00:00.353'
'2011/12/15 09:00:00.355'
'2011/12/15 09:00:00.359'
'2011/12/15 09:00:00.373'
'2011/12/15 09:00:00.402'
'2011/12/15 09:00:00.407'
'2011/12/15 09:00:00.437'
'2011/12/15 09:00:00.437'
'2011/12/15 09:00:00.437'
Fangjun Jiang
Fangjun Jiang 2011-12-19
And the variable dates is a 2x1 cell array. It should be representative to your 200x1 cell array.
Fangjun Jiang
Fangjun Jiang 2011-12-19
Change the last column symbol ":" in the format string to ".". Your data is different than you described in your question. Jan was right. It usually is HH:MM:SS.FFF, not HH:MM:SS:FFF
Fangjun Jiang
Fangjun Jiang 2011-12-19
Or you don't need to specify the format anymore since it is standard.
%%
Dates={'2011/12/15 09:00:00.039';'2011/12/15 09:00:00.039'};
datenum(Dates)

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Walter Roberson
Walter Roberson 2011-12-19

0 个投票

datenum(YourArray, 'yyyy/mm/dd HH:MM:SS.FFF')
See http://www.mathworks.com/help/techdoc/matlab_prog/bspgcx2-1.html#bsplnu3-1

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Syed Abbas
Syed Abbas 2011-12-19
I get the following error when I use datenum():
Error using datenum (line 181)
DATENUM failed.
Caused by:
Error using dtstr2dtnummx
Failed on converting date string to date number.
datenum() works if I have a single date but I have a date variable of type [200 x 1 cell] and want to convert all the dates in this variable at once
Walter Roberson
Walter Roberson 2011-12-19
What does size() and class() show for the first element of your cell array, YourCell{1} ?
Are the strings absolutely consistent?
What happens if you try
cellfun(@(S) datenum(S, 'yyyy/mm/dd HH:MM:SS.FFF'), YourCell)
At the moment, it seems to me that either you do not have a cell array of strings, or else that at least one of the entries is not in the expected format.
Syed Abbas
Syed Abbas 2011-12-19
size shows 1 23 and class shows char
Syed Abbas
Syed Abbas 2011-12-19
I get the following error with cell fun:
Error using cellfun
Input #2 expected to be a cell array, was char instead.

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0 个投票

Hello.
>> A={'2011/12/19 13:27:50.890';'2012/12/19 18:49:40.790'}
A =
'2011/12/19 13:27:50.890'
'2012/12/19 18:49:40.790'
>> vector=datevec(A, 'yyyy/mm/dd HH:MM:SS.FFF')
vector =
1.0e+003 *
2.0110 0.0120 0.0190 0.0130 0.0270 0.0509
2.0120 0.0120 0.0190 0.0180 0.0490 0.0408
Jan
Jan 2011-12-19

0 个投票

A less intelligent, but much faster method than DATENUM:
dates = {'2011/11/11 11:11:11.111'; ...
'2012/12/12 12:12:12.121'};
function Vector = myDateConversion(DateCell)
S = sprintf('%s ', DateCell{:});
D = sscanf(S, '%d/%d/%d %d:%d:%f');
Vector = transpose(reshape(D, 6, []));
On Matlab 2009a this is 5 times faster than datevec(dates, 'yyyy/mm/dd HH:MM:SS.FFF'), but datevec is much smarter and converts the '2011/32/12' correctly.
The date topic has been discussed in Mike's blog recently:
http://blogs.mathworks.com/desktop/2011/11/28/using-dates-in-matlab/

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