How to find max value and divide it in two rows

I have matrix X as follows:

X = [66  101  1050  1200
66  102  1200  1370
66  106  1370  1450
67  103  1050  1060
67  105  1060  1190
67  105  1190  1450
68  101  1000  1050
68  102  1050  1400
69  103  1200  1265
69  104  1265  1600];

I want to check the forth column in last row belong to the every different ID (e.g. row 3, 6, 8 & 10) and check if they are <=1400 or not. If they are larger than 1400 then the difference with 1400 should be calculated and a new row added to the matrix. In new row, first and second arrays from previous row should be repeated, and third array should be 1000 and forth array should be 1000+the difference found earlier.

Answer 1

[Andrei Bobrov]

X = [66 101 1050 1200
66 102 1200 1370
66 106 1370 1450
67 103 1050 1060
67 105 1060 1190
67 105 1190 1450
68 101 1000 1050
68 102 1050 1400
69 103 1200 1265
69 104 1265 1600];

t0 = accumarray(findgroups(X(:,1)),1);
ii = cumsum(t0);
t = X(ii,4) > 1400;

a = t0+t;
iend = cumsum(a);
idx = true(iend(end),1);
idx(iend(t)) = false;
out = zeros(iend(end),size(X,2));
out(idx,:) = X;
jj = find(~idx);
out(jj,:) = out(jj-1,:);
out(jj,3) = 1000;
out(jj,4) = out(jj,4) - 1400 + 1000;

[Xie]

out(jj-1,4) = 1400;