# We have a matrix containing the year month and day of data points. We want to find out how often each day occurs. Thanks in advance!

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Leon Garger 2016 年 12 月 12 日

We want to know how often a day repeats.

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### 回答 (2 件)

Isabella Osetinsky-Tzidaki 2016 年 12 月 12 日

% A is N by 3 matrix (y,M,d)
B=datetime(A,'Format','yyyyMMdd');
C=char(B);
D=str2num(C);
F=unique(D);
L=length(F);
Answer=nan(L,2); % pre-allocate date and its occurrence columns
for i=1:L
n=length(find(D==F(i)));
Answer(i,:)=[F(i) n];
end
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Star Strider 2016 年 12 月 12 日
Another approach:
M = [2016 12 12; 2016 12 11; 2016 12 11; 2016 12 10]; % Create Data
dn = datenum( M ); % Compute Date Numbers
[Ud,ia,ic] = unique(dn, 'stable'); % The 'stable' Argument Retains The Original Order
date_tally = accumarray(ic, 1); % Count Occurrences
Result = [M(ia,:), date_tally]
Result =
2016 12 12 1
2016 12 11 2
2016 12 10 1
You will need to make appropriate changes for the format of your dates (you did not specify what they were). This should do what you want.

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