Highlighting different part of graph

I have this graph, represented as a vector

I am analyzing this signol for regions of interest, and I'm saving these positions as another vector. Let's say I get a vector such as

V=[1,...,10, 20,...25, 70,...,124]

(never mind why those regions are interesting, just an example). How do i highlight these regions in my graph in an easy way, i.e., so i can get something like

(again, never mind where those regions actually are). I've tried something like

figure()
hold on
plot(signal)
plot(V,signal(V),'r','LineWidth',1.5)

But I only end up with

I have ideas on how to solve this by spliting the vector and saving as a cell, but I'm wondering if anyone else has a simpler solution.

Answer 1

[Star Strider]

The likely solution is to add an independent variable vector:

x = 0:numel(signal)-1;                              % Independent Variable Vector

figure()
hold on
plot(x, signal)
plot(x(V) ,signal(V),'r','LineWidth',1.5)

.