What does "IND" do?

Could someone please explain what is the meaning behind the following sequences? I don't quite understand the meaning of the "ind" function.

Thank you!

P.S. I don't know whether it is worth mentioning, but the code was written using Octave.

-------------------------

indBl=[];
%
if (Blt(1) == 1)
    indBl=[indBl 1];  
end
if (Blr(1) == 1)
    indBl=[indBl 2];  
end
%
if (Blt(2) == 1)
   indBl=[indBl 2*NE1+1];  
end
if (Blr(2) == 1)
   indBl=[indBl 2*NE1+2];  
end
%
if (Blt(3) == 1)
   indBl=[indBl 2*NE+1];   
end
if (Blr(3) == 1)
   indBl=[indBl 2*NE+2];   
end

Answer 1

[Walter Roberson]

There is no "ind" function in that code.

What the code is doing is adding values to the end of a list.

If Blt(1) is 1, then add 1 to the end of the list.

Then if Blr(1) is 1, add 2 to the end of the list (that might have been updated in the previous step.)

Then if Blt(2) is 1, add 2*NE1+1 to the end of the list.

And so on.

The [] is the same as horzcat() for this purpose, so you could write it as

if Blt(1) == 1
    indBl = horzcat(indBl, 1);
end

You could also write it as

if Blt(1) == 1
    indBl(end+1) = 1;
end

[Alice Marin]

Thank you for the clarification!