Usually the X is strike price and Y is IV, creating an IV "wedge". However if you want to see how this is compared to last week you'd have to make another wedge. Which could be a pain if you want to see a large time frame. The only way I can see this is with a 3d graph - with the 3rd dimension as expiration. Looks weird. I hate 3d graphs.. But I guess there's no other choice?
3D is too complicated for me. This graph is from SILEXX. It has no value for me. When I was a MM I used LIVEVOL PRO to track current and past IVOL. I prefer data to pictures.
I find both useful, but one objection against 3D seems that in 3D some data can get overshadowed (covered, hided) by other data, especially if there are "waves" in the chart.
I prefer using 3-D Scatter plots without interpolation (plotly express is a good tool for this). However, there are some sticky wickets that cloud clear observations, such as the typical use of Calendar VS Trading days that will product artifacts in your shorter terms that are not really there when using Calendar days. As Robert states, it may be wise to not rush into taking what you think you observe as actionable.
Here's how we present it: https://gyazo.com/c940d165255678f37ceafdf5f9c11d4a And then look at constant maturity at different delta levels. Bottom right is the term structure picture. https://gyazo.com/2d708cd699b3511030d678bf83ba4c5e
I no longer trade changes in IVOL based on Supply-Demand changes. When I did, I never looked at the entire curve. I looked at the differences between the 25 Delta call and put and cared when that changed from where it typically traded. That meant there where large orders to buy or sell changing the relationship. I found meaning in that. I also monitored past IVOL before and after events like earnings to predict where it might go after the event. When I look at that 2D curve, I see the same smile as every stock and stock index. When I look at the 3D one, I see a pretty blanket that I have no idea how to make money from. But like I said, I can only handle simple strategies where I can make a small amount of money over and over with little risk.
The biggest thing I see is the skew or what we call slope. It is the bottom chart below: https://gyazo.com/e7162e95a6d504ebee3d1719349e512e Notice how low it is in a graph that spans back to 2007. My take: It is the effect of the 0DTE where market makers no longer are stuck in the systematic short put, long call position.
I got a stupid question. Is it possible to track a specific spread combination over a time period with that? Say you want a Jan'24/Feb'24 Calendar. You can probably look for the historical price with IV of that specific combo right?