extract certain lines in matrice

hi everyone i have this matrice

 0.8979    0.8979    0.8979    0.8979    0.8979    0.8979    0.8979    0.8979
    0.5934   -0.5934    0.5934   -0.5934    0.5934   -0.5934    0.5934   -0.5934
    0.5934    0.5934   -0.5934   -0.5934    0.5934    0.5934   -0.5934   -0.5934
    0.8979   -0.8979   -0.8979    0.8979    0.8979   -0.8979   -0.8979    0.8979
    0.5934    0.5934    0.5934    0.5934   -0.5934   -0.5934   -0.5934   -0.5934
    0.8979   -0.8979    0.8979   -0.8979   -0.8979    0.8979   -0.8979    0.8979
    0.8979    0.8979   -0.8979   -0.8979   -0.8979   -0.8979    0.8979    0.8979
    0.5934   -0.5934   -0.5934    0.5934   -0.5934    0.5934    0.5934   -0.5934

I want to extract the line 1&2&4&7 in order to put them in another equation can anyone give me the code to put certain lines in another place

Answer 1

[Guillaume]

This is very basic matrix indexing which is covered in the Getting started tutorial:

m = [0.8979    0.8979    0.8979    0.8979    0.8979    0.8979    0.8979    0.8979
  0.5934   -0.5934    0.5934   -0.5934    0.5934   -0.5934    0.5934   -0.5934
  0.5934    0.5934   -0.5934   -0.5934    0.5934    0.5934   -0.5934   -0.5934
  0.8979   -0.8979   -0.8979    0.8979    0.8979   -0.8979   -0.8979    0.8979
  0.5934    0.5934    0.5934    0.5934   -0.5934   -0.5934   -0.5934   -0.5934
  0.8979   -0.8979    0.8979   -0.8979   -0.8979    0.8979   -0.8979    0.8979
  0.8979    0.8979   -0.8979   -0.8979   -0.8979   -0.8979    0.8979    0.8979
  0.5934   -0.5934   -0.5934    0.5934   -0.5934    0.5934    0.5934   -0.5934];

subm = m([1 2 4 7], :); %select all columns of rows 1, 2, 4 and 7

[Dija]

thank you