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Jan 7 at 23:07 comment added Sextus Empiricus Is the underlying process truly a Gaussian process with a continuous kernel? This jump around 0.950 seems more like a change in the trend. If you are after a non-stationary process then you might try to model the process by $y(x) = f(x) + \epsilon(x)$ where $f(x)$ is some decreasing function (the non-stationary part), and $\epsilon(x)$ is a noise term based on a Gaussian process.
Jan 7 at 21:55 comment added Ben Bolker Don't know if it's Python code or not, but see: Riihimäki, Jaakko, and Aki Vehtari. 2010. “Gaussian Processes with Monotonicity Information.” In Proceedings of the Thirteenth International Conference on Artificial Intelligence and Statistics, 645–52. JMLR Workshop and Conference Proceedings. proceedings.mlr.press/v9/riihimaki10a.html.
Jan 7 at 21:09 answer added marnix timeline score: -1
Mar 4, 2019 at 3:56 vote accept Mathews24
Mar 3, 2019 at 4:11 answer added j__ timeline score: 8
Mar 1, 2019 at 19:33 comment added Mathews24 @Yves That is certainly the idea I'm trying to capture. Although perhaps this is where an example Python code applied on the above would help as I'm a bit unclear on specifics (e.g. application of knots in GPR, actual implementation of linear inequality constraints in code).
Mar 1, 2019 at 19:08 comment added Mathews24 @kjetilbhalvorsen The primary reason for applying GPR is obtain accurate uncertainty estimates which are critical to my work. GPR does have a well-defined analytic derivative, although it is based upon the chosen kernel.
Mar 1, 2019 at 16:41 comment added Yves This may help.
Mar 1, 2019 at 16:04 comment added Mathews24 @Yves Ideally both. I would like to understand how, in both theory and code, to enforce monotonicity for the above example.
Mar 1, 2019 at 14:30 comment added kjetil b halvorsen Is there some specific reason you need to use gaussian processes? If not, consider using monotone splines, see. As far as I remember, most gaussian processes do not even have derivatives, so to enforce monotonicity, I guess you at least wil need a kernel giving derivatives, and then restrict those to be positive. But I beleive that gaussian processes with derivatives are very smooth, maybe too smooth!
Mar 1, 2019 at 7:51 comment added Yves Are you looking for some theoretical elements on this (rather complex) problem or simply for an existing code in Python?
Mar 1, 2019 at 6:21 history edited Mathews24 CC BY-SA 4.0
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Mar 1, 2019 at 6:15 history asked Mathews24 CC BY-SA 4.0