what it does mean?

If index(1,1)==1

S1=0;

S2=1;

end

Answer 1

[Cris LaPierre]

See MATLAB Onramp, in particular Chs 2, 5, 8, 12 & 13.

Answer 2

[David Hill]

If the matrix 'index' indexed at (1,1) equals 1, then assign S1 =0 and S2 = 0.

if index(1,1)==1
    S1=0;
    S2=1;
end

[Nyam Jargalsaikhan]

A=[1 5 7 8 4 2 6 3];

[~, index]=sort(A);

if index(1,1)==1

S1=0;

S2=0;

end

if index(1,1)==2

S1=0;

S2=0;

end

if index(1,1)==3

S1=0;

S2=0;

end

what about this one?

[David Hill]

Matlab has good documentation. You should look at the sort() function.

help sort

You will see that the index array contains the index numbers for rearraigning A to sort it.

A(index)==sort(A);

The code above seems poorly written. First, index is only one dimension, so you only need to index at (1). Second, all if statements do the same thing so combining them into a single statement would be better.

A=[1 5 7 8 4 2 6 3];
[~, index]=sort(A);
if ismember(index(1),[1 2 3])
    S1=0;
    S2=0;
end