Logical indexing returns different dimensions

a = [3, 2]

a = 1×2

3 2

b = [1; 1] == 1

b = 2×1 logical array
   1
   1

a(b) % returns a 1x2 array

ans = 1×2

3 2

a = [3, 2; 4, 5]

a = 2×2

3 2 4 5

b = [1; 1; 1; 1] == 1

b = 4×1 logical array
   1
   1
   1
   1

a(b) % returns a 4x1 array

ans = 4×1

3 4 2 5

[Umesh Kumar Singla]

I was expecting both to return 1 x n type arrays but that's not the case. Am I missing something?

Answer 1

[Matt J]

Vectors have different indexing behavior than matrices. There's nothing more to it, except perhaps to point out that it's not just logical indexing. It applies to regular indexing as well:

a=[10,20,30,40];
a([1;2])

ans = 1×2

10 20

a=[10,20;30 40];
a([1;2;3;4])

ans = 4×1

10 30 20 40