Create new variable that recognizes changes in a code in Matlab - matlab

Question

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 match the ones in C2 from variable B.
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 }

Answer 1

AB = {'Y' 'Initial' 'C2' 'Change' 'C2'}; % initialize result cell array
for i=2:size(A,1) % loop through rows of A
indicesOfChanges = find(diff([A{i,2:end}])); % find changes in row
for j=1:length(indicesOfChanges) % for all changes look up the corresponding values
ind1=find(B(:,2)==A{i,indicesOfChanges(j)+1}); % row index in B of value before change
ind2=find(B(:,2)==A{i,indicesOfChanges(j)+2}); % row index in B of value after change
AB{end+1,1} = A{i,1};
AB{end,2} = B(ind1,2);
AB{end,3} = B(ind1,3);
AB{end,4} = B(ind2,2);
AB{end,5} = B(ind2,3);
end
end
Maybe this could be further improved by using a vectorized approach, but as long as your arrays aren't too big it should work fast enough using loops.