Would like a script that removes repeat data

Question

BA 2022-9-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1810935-would-like-a-script-that-removes-repeat-data

评论： BA 2022-9-23

Dataset.xlsx

I'm looking to create a script that removes dates that repeat one after the other. For some reason, the program I used to collect the data does something stupid where they send a prompt twice on the same day, but I only want the program to be sent once. For the repeat dates, I want those dates to be deleted. For example:

Dates_Wrong = ['2/4/21';'2/5/21';'2/5/21';'2/6/21';'2/7/21']
Dates_Wrong = 5×6 char array
    '2/4/21'
    '2/5/21'
    '2/5/21'
    '2/6/21'
    '2/7/21'

You can see here, the 2/5/21 date repeats. I would like to create a script that eliminates that repeat data.

The hard part is that you can't just do unique(x) on the entire dates column because there are different subjects with repeating dates and that is why I'm having trouble. It has to be something where it identifies 2 repeating dates in sequence and removes the more recent date. Here is an example of what our previous dates would look like with the repeat date removed.

Dates_Right = ['2/4/21';'2/5/21';'2/6/21';'2/7/21']
Dates_Right = 4×6 char array
    '2/4/21'
    '2/5/21'
    '2/6/21'
    '2/7/21'

This is sort of what I was thinking of doing but I'm not sure if it makes sense

for x=1:length(MorningPrompt.SurveyStartedDate)
    if x-1==x                       %This is where I'm having trouble. I think the rest of the script is fine but I'm not sure how to use this part to account for strings since x isn't the actually string found within that variable
        MorningPrompt(x,:) = [];
    end
end

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Answer 1

Steven Lord 2022-9-23

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https://ww2.mathworks.cn/matlabcentral/answers/1810935-would-like-a-script-that-removes-repeat-data#answer_1059485

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Dates_Wrong = ['2/4/21';'2/5/21';'2/5/21';'2/6/21';'2/7/21']
Dates_Wrong = 5×6 char array
    '2/4/21'
    '2/5/21'
    '2/5/21'
    '2/6/21'
    '2/7/21'
dt = datetime(Dates_Wrong, 'InputFormat', 'M/d/yy')
dt = 5×1 datetime array
   04-Feb-2021
   05-Feb-2021
   05-Feb-2021
   06-Feb-2021
   07-Feb-2021
differences = diff(dt)
differences = 4×1 duration array
   24:00:00
   00:00:00
   24:00:00
   24:00:00
repeated = differences ~= 0
repeated = 4×1 logical array
   1
   0
   1
   1

Note that differences and repeated are both one element shorter than dt. Add a true as the first or last element depending on whether you always want to keep the first element or the last.

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BA 2022-9-23

在 MATLAB Online 中打开

Thank you! This is wonderful.

Just had a few questions.

1) Since I want the first value of each of the repeats, would I just have to set the last line of the logical array to be 1?

2) For the logical indexing, this is the command I'm using. I think it works but its the first time I've used logical indexing so I'm not sure

%My code adapted using your code
Dates = Dataset.Dates;
dt = datetime(Dates, 'InputFormat', 'M/d/yy');
differences = diff(dt);
repeated = differences ~= 0
%Indexing
NonRepeats = Dataset(repeated(:,1)==1, :);