Since futures trade on a contract by contract basis, how can you plot the price over an extended period of time? As a reference I have included a plot of VX futures (VIX CBOE volatility index) from investing.com:
How do you determine when to roll from one contract to the other? Also is there not a price difference from the contract which is expiring and the one that is being rolled forward to? but yet there are no sudden price discontinuities in the charts.
Could anyone please explain what the method of extracting a continuous price series from a compilation of individual month by month contacts is?