what it is this meaning

j=size(r_ed,2):-1:1;

Answer 1

[Torsten]

It's a vector starting with the number of columns of the matrix r_ed and counting down to 1 in steps of -1.

E.g. if r_ed is (5x7), j is [7 6 5 4 3 2 1].

Best wishes

Torsten.