How can I add a simple plane on an "mgcViz" 3D plot?-CodePudding

I have the following code in R which draws a 3D plot

library(mgcViz)
library(rgl)
n <- 500
x <- rnorm(n); y <- rnorm(n); z <- rnorm(n)
ob <- (x-z)^2   (y-z)^2   rnorm(n)
b <- gam(ob ~ s(x, y, z))
b <- getViz(b)

plotRGL(sm(b, 1), fix = c("z" = 0), residuals = TRUE)

The here is the graph that I create:

How can I add a simple horizontal plane on z=5?

CodePudding user response：

You can use the planes3d() function from rgl to do that. It uses the plane equation $a x b y c z d = 0$, so z=5 would have a=0, b=0, c=1, d=-5. For example,

library(mgcViz)
#> Loading required package: mgcv
#> Loading required package: nlme
#> This is mgcv 1.8-40. For overview type 'help("mgcv-package")'.
#> Loading required package: qgam
#> Loading required package: ggplot2
#> Registered S3 method overwritten by 'GGally':
#>   method from   
#>    .gg   ggplot2
#> Registered S3 method overwritten by 'mgcViz':
#>   method from  
#>    .gg   GGally
#> 
#> Attaching package: 'mgcViz'
#> The following objects are masked from 'package:stats':
#> 
#>     qqline, qqnorm, qqplot
library(rgl)
n <- 500
x <- rnorm(n); y <- rnorm(n); z <- rnorm(n)
ob <- (x-z)^2   (y-z)^2   rnorm(n)
b <- gam(ob ~ s(x, y, z))
b <- getViz(b)

plotRGL(sm(b, 1), fix = c("z" = 0), residuals = TRUE)
planes3d(0,0,1,-5, col = "gray")

^{Created on 2022-06-24 by the reprex package (v2.0.1)}

Note that you can set the plane to be semi-transparent by setting an alpha value between 0 and 1, but rgl doesn't handle intersecting transparent objects very well, so it's unlikely to give nice results.

It also appears that rgl isn't working so well with reprex. You shouldn't see the doubled axis labels. This is fixed in the devel version available on Github.