What does Sel do in this code?

Hey all, I am a chemical engineering student researching how to model a distillation column. I have a found a code that does this, but I'm not sure what's happening in it.

[t,x]=ode15s('cola_lv',[0 20000],0.5*ones(1,82)');

Xinit = x(sel(size(x),1,1),:)';

I understand everything here except this "sel" command. I've never heard of it in during my studies. What exactly is it doing? I also cannot seem to use this command in my version of Matlab (2020b). Is this a package command, and if so, where do I go to download it?

[KSSV]

From where you got this code?

Answer 1

[Walter Roberson]

http://matrix.etseq.urv.es/manuals/matlab/toolbox/mutools/sel.html

Very old MATLAB!

It looks to me as if is just doing indexing. I think it is equivalent of

Xinit = x(end,:).';