Fill the column with pre-defined time intervals

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Damith 2015-2-20

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评论： Damith 2015-2-25

采纳的回答： Star Strider

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Hi,

I need to fill the column A below with pre-defined time intervals for each day. For example, Jan 1 1998

1/1/1998 0:00
1/1/1998 3:00
1/1/1998 4:00
1/1/1998 6:00
1/1/1998 9:00
1/1/1998 10:00
1/1/1998 12:00
1/1/1998 15:00
1/1/1998 16:00
1/1/1998 18:00
1/1/1998 21:00
1/1/1998 22:00
1/2/1998 0:00

A=

    1/1/1998 0:00
    1/1/1998 4:00
    1/1/1998 6:00
    1/1/1998 10:00
    1/1/1998 12:00
    1/1/1998 16:00
    1/1/1998 18:00
    1/1/1998 22:00
    1/2/1998 0:00
    1/2/1998 4:00
    1/2/1998 6:00
    1/2/1998 12:00
    1/2/1998 18:00
    1/3/1998 0:00
    1/15/1998 18:00
    1/16/1998 0:00
    1/16/1998 6:00
    1/16/1998 12:00
    1/16/1998 18:00
    1/17/1998 0:00
    1/17/1998 6:00
    1/17/1998 12:00
    1/17/1998 18:00
    1/18/1998 0:00
    1/18/1998 6:00
    1/18/1998 12:00
    1/18/1998 18:00
    1/19/1998 0:00
    1/19/1998 6:00
    1/19/1998 12:00
    1/19/1998 18:00
    1/20/1998 0:00
    1/20/1998 6:00
    1/20/1998 12:00
    1/20/1998 18:00
    1/21/1998 0:00
    1/21/1998 6:00
    1/21/1998 12:00
    1/21/1998 18:00
    1/22/1998 0:00
    1/22/1998 6:00
    1/22/1998 12:00
    1/22/1998 18:00
    1/23/1998 0:00
    1/23/1998 6:00
    1/22/1998 10:00
    1/22/1998 12:00
    1/22/1998 18:00
    1/22/1998 22:00
    1/23/1998 0:00

Is there a way to this MATLAB?

Thanks in advance.

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Answer 1

Star Strider 2015-2-20

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One way to do it:

D0 = datenum([1998 01 01]);
DT = 1/24;                          % Days/Hour
DM = eomday(1998,01);               % Days In January
DV = D0 + cumsum([0; ones(24*DM,1)*DT]);
Jan1998 = datestr(DV(1:end-1), 'mm/dd/yyyy HH:MM');
Result = [Jan1998(1:5,:); Jan1998(end-4:end,:)]         % Check Result

produces:

Result =
01/01/1998 00:00
01/01/1998 01:00
01/01/1998 02:00
01/01/1998 03:00
01/01/1998 04:00
01/31/1998 19:00
01/31/1998 20:00
01/31/1998 21:00
01/31/1998 22:00
01/31/1998 23:00

The ‘Result’ variable just looks at the first and last 5 entries.

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Star Strider 2015-2-20

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I need leading zeros on everything, but once I supplied them, my idea works:

D0 = datenum([1998 01 01]);
DT = 1/24;                          % Days/Hour
% DM = eomday(1998,01);               % Days In January
DM = 2;
DV = D0 + cumsum([0; ones(24*DM,1)*DT]);
Jan1998 = datestr(DV(1:3:end-1), 'mm/dd/yyyy HH:MM');
% Result = [Jan1998(1:5,:); Jan1998(end-4:end,:)]         % Check Result
A= ['01/01/1998 00:00'
    '01/01/1998 04:00'
    '01/01/1998 06:00'
    '01/01/1998 10:00'
    '01/01/1998 12:00'
    '01/01/1998 16:00'
    '01/01/1998 18:00'
    '01/01/1998 22:00'
    '01/02/1998 00:00'
    '01/02/1998 04:00'
    '01/02/1998 06:00'
    '01/02/1998 12:00'
    '01/02/1998 18:00'
    '01/03/1998 00:00'];
A = unique([Jan1998; A], 'rows');

produces:

A =
01/01/1998 00:00
01/01/1998 03:00
01/01/1998 04:00
01/01/1998 06:00
01/01/1998 09:00
01/01/1998 10:00
01/01/1998 12:00
01/01/1998 15:00
01/01/1998 16:00
01/01/1998 18:00
01/01/1998 21:00
01/01/1998 22:00
01/02/1998 00:00
01/02/1998 03:00
01/02/1998 04:00
01/02/1998 06:00
01/02/1998 09:00
01/02/1998 12:00
01/02/1998 15:00
01/02/1998 18:00
01/02/1998 21:00
01/03/1998 00:00

that I believe is what you want.

You will have to adapt it to your particular application, supplying ‘A’ with leading zeros where necessary, so each numeric field is of the appropriate length. Otherwise, it won’t work.

Star Strider 2015-2-20

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@Damith — I would use the datenum function to convert them to double. My ‘DV’ variable already does that, so you can use it with the datenum output of your dates, and the unique call in my code should work the same. (There is always the potential problem of slight mismatches due to approximation errors in floating-point operations, but with the dates as you have defined them, that should not be a problem. The datenum representations of the hours should be unambiguous.)

My code then becomes:

D0 = datenum([1998 01 01]);
DT = 1/24;                          % Days/Hour
% DM = eomday(1998,01);               % Days In January
DM = 2;
DV = D0 + cumsum([0; ones(24*DM,1)*DT]);
DV = DV(1:3:end-1);
A= ['01/01/1998 00:00'
    '01/01/1998 04:00'
    '01/01/1998 06:00'
    '01/01/1998 10:00'
    '01/01/1998 12:00'
    '01/01/1998 16:00'
    '01/01/1998 18:00'
    '01/01/1998 22:00'
    '01/02/1998 00:00'
    '01/02/1998 04:00'
    '01/02/1998 06:00'
    '01/02/1998 12:00'
    '01/02/1998 18:00'
    '01/03/1998 00:00'];
A = unique([DV; datenum(A, 'mm/dd/yyyy HH:MM')]);
Result = datestr(A, 'mm/dd/yyyy HH:MM')

with the same ‘Result’ as before:

Result =
01/01/1998 00:00
01/01/1998 03:00
01/01/1998 04:00
01/01/1998 06:00
01/01/1998 09:00
01/01/1998 10:00
01/01/1998 12:00
01/01/1998 15:00
01/01/1998 16:00
01/01/1998 18:00
01/01/1998 21:00
01/01/1998 22:00
01/02/1998 00:00
01/02/1998 03:00
01/02/1998 04:00
01/02/1998 06:00
01/02/1998 09:00
01/02/1998 12:00
01/02/1998 15:00
01/02/1998 18:00
01/02/1998 21:00
01/03/1998 00:00

Damith 2015-2-21

No worries. Thanks.

Damith 2015-2-25

Star,

I have simplified the table now. Can you help me a way to this. I think it should be easy now.

https://www.mathworks.com/matlabcentral/answers/180349-select-rows-from-table-and-interpolate

Thanks in advance.

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Fill the column with pre-defined time intervals

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Fill the column with pre-defined time intervals

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