how to select multiple rows from a large matrix and leave 1 row every time

Hello friends,

Let's say we have a=[20,100];

what I want is to select three rows and leave 4th row then again select 3 rows from 5 to 7 then leave 8th likewise.

selected_rows= ([1:3, 5:7, 9:11, 13:15, 17:19],:) ;

selected_rows=[1 2 3 5 6 7 9 10 11 13 14 15 17 18 19]

but i dont know how to do it automatically I need to use for loop or is there any direct way to do this???

This is very basic question. But still I think may be I will write a long code for doing this.

Can you please suggest me any other way??

Thanks

Answer 1

[Ive J]

A = rand(20, 100);
keepRowsIdx = setdiff(1:size(A, 1), 4:4:size(A, 1));

  Columns 1 through 10

     1     2     3     5     6     7     9    10    11    13

  Columns 11 through 15

    14    15    17    18    19

newA = A(keepRowsIdx, :);

[Ankita Jindal]

thank you so much