Create new variable that recognizes changes in the code

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Maria 2014-7-22

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https://ww2.mathworks.cn/matlabcentral/answers/142933-create-new-variable-that-recognizes-changes-in-the-code

评论： Geoff Hayes 2014-7-24

采纳的回答： Geoff Hayes

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I have a double matrix B that has in C1 the year 1998 and in C2 a code (unrepeated). Each C2 is given a value in C3.

%   C1      C2   C3
B=[ 1998    22   37 
1998    34    7
1998    76    12
1998    98    29
1998    107   14    
…]

This is how I got to B:

N1=[N{:,1} N{:,2} N{:,3}];
N1=unique(N1(:,1:3),'rows'); 
N3= unique(N1(:,1:2),'rows'); 
for m=1:size(N3,1)
    N3(m,3)=sum(N1(:,1) == N3(m,1) & N1(:,2)==N3(m,2));
end
B=N3((N3(:,1) == 1998),:);

I have a cell-array A with the years horizontally disposed in R1, un-repeated values in Y, and corresponding codes in the columns that follow. The codes are the same as in C2 from variable B, but disposed differently.

A={Y  1996 1997 1998 1999  %R1
1   107 107 22  22  
13  98  98  76  1267 
… }

Is there a way I could get a new variable that recognizes the change in the codes in variable A, and presents the corresponding values from C3 in B? For instance:

AB={Y Initial C2 Change C2
1   107 14  22  37
13  98  29  76  12 }

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采纳的回答

Geoff Hayes 2014-7-22

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https://ww2.mathworks.cn/matlabcentral/answers/142933-create-new-variable-that-recognizes-changes-in-the-code#answer_146014

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Given the A and B from above (less the incomplete portions), you could iterate over each row of A and compare the second and fourth values with that from distinct second column of B, looking for a match. If a match is found, then replace the third and fifth values form AB with those from B (if a match for both can be found)

 % initialize AB to that of A
 AB = A;
 % iterate over each row of A
 for k=1:size(A,1)
    % search the second column of B for the second element of A
    idx = find(B(:,2)==A{k,2});
    if ~isempty(idx)
        % replace
        AB{k,3} = B(idx,3);
    else
        % not found, so set to empty (?)
        AB{k,3} = [];
    end
    % search the second column of B for the fourth element of A
    idx = find(B(:,2)==A{k,4});
    if ~isempty(idx)
        % replace
        AB{k,5} = B(idx,3);
    else
        % not found, so set to empty (?)
        AB{k,5} = [];
    end
 end