在 Matlab 数组的每一行中索引相同/不同的元素

Question

Suppose I have a IxJ matrix A in Matlab which contains some numbers (possibly, including Inf , -Inf ).

For example, for I=3 and J=6 , I could have

A=  [0    0      Inf -Inf 0   1; 
     5    4      Inf -Inf 6   5;
     Inf -Inf    0    Inf 0   2];

I want to construct a matrix B of size IxJ , such that each row i starts from 1 , adds a +1 every time an element of A(i,:) changes, and assigns equal index to equal elements. Two Inf elements have to be treated as equal. Similarly, two -Inf elements have to be treated as equal.

In the example above

B=  [1 1 2 3 1 4;  %
     1 2 3 4 5 1;
     1 2 3 1 3 4];

Could you advise on how to proceed?

Answer 1

A simple approach is to use the third output of unique with the 'stable' option for each row:

B = NaN(size(A)); % preallocate
for k = 1:size(A,1)
   [~, ~, B(k,:)] = unique(A(k,:), 'stable');
end