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library(plot3D)

## Warning: package 'plot3D' was built under R version 3.6.2

library(plot3Drgl)

## Warning: package 'plot3Drgl' was built under R version 3.6.2

## Loading required package: rgl

## Warning: package 'rgl' was built under R version 3.6.2

# x, y, z variables
x <- mtcars$wt
y <- mtcars$disp
z <- mtcars$mpg
# Compute the linear regression (z = ax + by + d)
fit <- lm(z ~ x + y)
# predict values on regular xy grid
grid.lines = 26
x.pred <- seq(min(x), max(x), length.out = grid.lines)
y.pred <- seq(min(y), max(y), length.out = grid.lines)
xy <- expand.grid( x = x.pred, y = y.pred)
z.pred <- matrix(predict(fit, newdata = xy), 
                 nrow = grid.lines, ncol = grid.lines)
# fitted points for droplines to surface
fitpoints <- predict(fit)
# scatter plot with regression plane
#library(rgl)

scatter3D(x, y, z, pch = 18, cex = 2, 
    theta = 20, phi = 20, ticktype = "detailed",
    xlab = "wt", ylab = "disp", zlab = "mpg",  
    surf = list(x = x.pred, y = y.pred, z = z.pred,  
    facets = NA, fit = fitpoints), main = "mtcars")

#plotrgl()