Use an array containing indexes to extract a subset of larger array

largeArray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

indexes = [5,9,16]

% use the indexes array to extract 3 elements at each index in the largeArray to yield:

subSetArray = [5,6,7 ; 9,10,11; 16,17,18]

[Jeffrey Clark]

@Scorp, attack problems like this by looking at what you have and then what you want. I won't give you the answer here:

>>largeArray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
largeArray =

  Columns 1 through 17

     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16    17

  Columns 18 through 20

    18    19    20
    
>>indexes = [5,9,16]
indexes =

     5     9    16

>>subSetArray = [5,6,7 ; 9,10,11; 16,17,18]
subSetArray =

     5     6     7
     9    10    11
    16    17    18
    
>>note = indexes' % apostrophy converts arrays (look it up)
note =

     5
     9
    16
    
>>also = 2+indexes' % compare with subSetArray
also =

     7
    11
    18

Answer 1

[Voss]

largeArray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

largeArray = 1×20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

indexes = [5,9,16]

indexes = 1×3

5 9 16

% use the indexes array to extract 3 elements at each index in the largeArray to yield:
% subSetArray = [5,6,7 ; 9,10,11; 16,17,18]
subSetArray = largeArray(indexes(:)+(0:2))

subSetArray = 3×3

5 6 7 9 10 11 16 17 18

Make sure you don't go off the end of largeArray:

indexes = [5,9,19]

indexes = 1×3

5 9 19

subSetArray = largeArray(indexes(:)+(0:2))

Index exceeds the number of array elements. Index must not exceed 20.