Use "find" function in "datetime"

Question

RG 2023-10-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2035504-use-find-function-in-datetime

回答： Sulaymon Eshkabilov 2023-10-18

I have some entries as datetime class. I am trying to get the id where the entry for date is "2016-02-18 00:00:00" for instance. I know I have the exact point there but the id is empty. It works for some other columns of datetime but for one of them does not work!

id=find(time=='2016-02-18 00:00:00')

id = 0×1 empty double column vector

I appreciate any help.

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Answer 1

Walter Roberson 2023-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/2035504-use-find-function-in-datetime#answer_1336149

在 MATLAB Online 中打开

T = [datetime(2016,2,18); datetime(2016, 2, 18, 0, 0, 0.1)]
T = 2×1 datetime array
   18-Feb-2016 00:00:00
   18-Feb-2016 00:00:00
id = find(T == '2016-02-18 00:00:00')
id = 1

Both entries display the same with the default format, but that does not mean they are equal.

T.Format = 'dd-MMM-yyyy HH:mm:ss.SSSSSS'
T = 2×1 datetime array
   18-Feb-2016 00:00:00.000000
   18-Feb-2016 00:00:00.100000
T2 = dateshift(T, 'start', 'second')
T2 = 2×1 datetime array
   18-Feb-2016 00:00:00.000000
   18-Feb-2016 00:00:00.000000
id2 = find(T2 == '2016-02-18 00:00:00')
id2 = 2×1
     1
     2

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Answer 2

Sulaymon Eshkabilov 2023-10-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2035504-use-find-function-in-datetime#answer_1336154

在 MATLAB Online 中打开

DATE_Data.txt

It looks like your imported data variable name may not be correctly assigned. Here is a plain example where datetime works ok:

%% Set up the Import Options and import the data
opts = delimitedTextImportOptions("NumVariables", 2);
% Specify range and delimiter
opts.DataLines = [2, Inf];
opts.Delimiter = "   ";
% Specify column Names and Types
opts.VariableNames = ["Time",     "Data"];
opts.VariableTypes = ["datetime", "double"];
% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";
opts.ConsecutiveDelimitersRule = "join";
opts.LeadingDelimitersRule = "ignore";
% Specify variable properties
opts = setvaropts(opts, "Time", "InputFormat", "yyyy-MM-dd HH:mm:ss");
% Import the data
D = readtable("DATE_Data.txt", opts); % Note that the imported data is a table variable
IDX=find(D.Time=='2016-02-18 00:00:00')
IDX = 2×1
     1
     4
% Check 
D(IDX,:)
ans = 2×2 table
       Time        Data 
    ___________    _____

    18-Feb-2016       13
    18-Feb-2016    23.23