Date Conversion

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,

[Jan]

Are you sure about the colon before the fractional seconds? Usually there is a dot.

[Syed Abbas]

Oh, that works now! I mistook the colun for the dot. Thansk a lot for ponting that out.

Answer 1

[Fangjun Jiang]

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

[Syed Abbas]

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]

Please post the inputs you are using.

[Syed Abbas]

I keep getting the same error I meantioned earlier

[Jan]

For which input? Please post an exact copy.

[Fangjun Jiang]

Copy the exact command in the answer. You see it worked fine on my computer.

[Syed Abbas]

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]

And the variable dates is a 2x1 cell array. It should be representative to your 200x1 cell array.

[Fangjun Jiang]

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]

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)

Answer 2

[Walter Roberson]

datenum(YourArray, 'yyyy/mm/dd HH:MM:SS.FFF')

See http://www.mathworks.com/help/techdoc/matlab_prog/bspgcx2-1.html#bsplnu3-1

[Syed Abbas]

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]

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]

size shows 1 23 and class shows char

[Syed Abbas]

I get the following error with cell fun:

Error using cellfun

Input #2 expected to be a cell array, was char instead.

Answer 3

[Jose Jeremias Caballero]

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

Answer 4

[Jan]

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/