MATLAB: Unknown operation performed.

unknown operation performed.

Hi,
I am new to MATLAB. the following is my code I am unable to understand
the operation perfromed B = S(A); and C = S(~A);
B has size 15×1 double
C has size 285×1 double
S is 20×15 double
A is 20×15 logical
my question is what operation has been performed in B and C and how did they get that size?
Please help me understand this!
clear all;
clc;
A = false( 20,9 );
sP = generate_pilots( 15 , 4, 'deterministic' );
G = [4:4:11 12:4:21]';
H = (2:7:20)';
A( G, H-1 ) = true;
S = zeros( size(A) );
B = S(A);
C = S(~A);
D = sP(1:15);
S( A ) = sP(1:15);
Regards,
Gnanesh

Best Answer

This is called logical (or boolean) indexing.
https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html
Your A matrix is filled with booleans.
B is now a vector that has all the elements of S that correspond to the same indexes as the Ones in A.
C is now a vector that has all the elements of S that correspond to the same indexes as the Zeros in A.
a = logical([1 0 0 1; 0 0 1 0])
s = [1,2,3,4;5,6,7,8]
s(a)
ans =
     1
     7
     4
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