What does the (:,6) do to "rx" in this code?
What is the 'r'? It looks like a name but it is not showing in the figure after the plot comes out.
It means: plot the 6th column of the array rx against t in red (r) with a dotted line (:).
But in such cases: The proof of the pudding is in the eating. Be courageous and test it out - the computer won't take damage.