How can I convert a datetime vector to cell??

Question

Adriano 2016-11-17

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评论： Peter Perkins 2016-11-18

采纳的回答： Walter Roberson

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hi all,

I have a vector of 4000 dates like:

25/07/1996;
26/07/1996;
29/07/1996;
30/07/1996;
31/07/1996;
01/08/1996;
02/08/1996;
05/08/1996;
06/08/1996;
07/08/1996;... and so on

Now, they are in datetime format. My goal is to insert the dates like rows names into a table. For example:

                  Age    Height    Weight    BloodPressure
                  ___    ______    ______    _____________
    25/07/1996     38     71        176       124     93   
    26/07/1996     43     69        163       109     77

I know that the rows names of a table must be cell inputs. Thus, how can I do it? Thanks a lot!

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Answer 1

Walter Roberson 2016-11-17

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编辑：Walter Roberson 2016-11-17

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Example:

YourTable = array2table((1:6).')
temp = cellstr( datestr(732430:732435) );
YourTable.Properties.RowNames = temp;

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Walter Roberson 2016-11-17

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YourTable = array2table((1:6).')
temp = cellstr( datestr(732430:732435, 'dd/mm/yyyy') );
YourTable.Properties.RowNames = temp;

I think you did not notice the datestr()

Adriano 2016-11-17

Great!!! Many thanks.

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Answer 2

Guillaume 2016-11-17

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Rather than using obsolete datestr, simply convert the datetime with char (which will use the Format of the datetime:

array2table(somematrix, 'RowNames', cellstr(char(datetimevector)))

Note that R2016b introduces the timetable that makes this even simpler:

array2timetable(somematrix, 'RowTimes', datetimevector)

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Peter Perkins 2016-11-18

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You can even go directly to a cellstr, without char in the middle:

array2table(somematrix, 'RowNames', cellstr(datetimevector))

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Answer 3

Peter Perkins 2016-11-18

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Adriano, row names are really convenient when you want to use them for subscripting. But in this case, you need to consider that you are taking a datetime vector and turning it into text. So you lose all the calendar arithmetic that datetime provides, and you will no longer be able to do things like

T(T.Date > '1-Jan-2016',:)

that you would be able to do if you put the datetime vector into your table as a variable rather than as the row names. It depends on what you want to do.

As Guillaume pointed out, the new-for-R2016b timetable type kind of gives you the best of both worlds, a timetable's "row names" are actually row times, stored as either datetimes or durations.