How to plot a set of densities in 3D using R?

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+6 Q:

How to plot a set of densities in 3D using R?

Hi!

I need to plot, in 3D, a set of densities associated to a time series. More precisely, I would like to be able in R to build an image close to this example alt text

This image is taken from [1]. The transparency plays an important role as let us see the trajectory of the "measures" in the x-y plane.

Any help will be greatly appreciated.

[1]: Juban and Kariniotakis, "Uncertainty Estimation of Wind Power Forecasts", presentation at EWEC 2008 - 01 April - Brussels, Belgium. (I can't post the link, google will help interested readers).

+3 A:

In 1996 I wrote a paper (published in JCGS) with a figure very similar to that but without the transparency. See http://robjhyndman.com/papers/estimating-and-visualizing-conditional-densities/ for the details. The plotting function is implemented in the R package hdrcde available on CRAN. The package contains some examples in the help files. You should be able to adapt my code to add the transparency.

Rob Hyndman 2010-07-21 09:22:38

Thanks!I'm looking into your code, but I think I need to master the persp function first... doesn't look as an easy task!

José Luis 2010-07-22 15:39:44

+4 A:

This is pretty, but is it really useful? Even with the transparency, it is very hard to track and compare different trajectories.

hadley 2010-07-21 12:45:43

Yes it is useful. The trick is not to track or compare trajectories, but to have a visual estimation of the uncertainty of a forecaster. The usefulness concept is very context dependent, and in my context such a pretty graph can be a very useful graph.

José Luis 2010-07-22 08:53:29

I am skeptical that this is the best plot for any task - the perceptual decoding of a rotated 3d plot like this is extremely difficult, not to mention the problems with foreground objects obscuring background objects.

hadley 2010-07-22 13:48:53

Would you suggest any alternative to display this information?

José Luis 2010-07-22 15:38:57

The third dimension (z-axis in this case) could be color. In your plot, it seems that color and height are conveying the same variable.

Vince 2010-07-26 18:43:55

I would think facetted line plots would be the way to go.

hadley 2010-07-27 01:18:24

+1 A:

This is how far I got thanks to Rob's hint. I used persp() to create an empty plot and added polygons and lines to it:

alt text

However, it is not as pretty as the original one... :(

José Luis 2010-07-23 13:04:39

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How to plot a set of densities in 3D using R?

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