Efficient colon operator for multiple start and end points

Question

Suppose I have the following two variables:

start_idx = [1 4 7];
end_idx   = [2 6 15];

I want to efficiently (no for loop

Answer 1

As I indicated in the comments, a one liner to solve this would be :

out=cell2mat(arrayfun(@(x,y)[x:y],start_idx,end_idx,'uniformoutput',false));

---

The arrayfun call will create a cell array whose each cell is a part of your output :

ans =

     1     2


ans =

     4     5     6


ans =

  Columns 1 through 8

     7     8     9    10    11    12    13    14

  Column 9

    15

By wrapping it inside a cell2mat call you get the expected output :

out =

  Columns 1 through 8

     1     2     4     5     6     7     8     9

  Columns 9 through 14

    10    11    12    13    14    15