5 dimensional plot in r

Question

I am trying to plot a 5 dimensional plot in R. I am currently using the rgl package to plot my data in 4 dimensions, using 3 variables as the x,y,z, coordinates, another variable as the color. I am wondering if I can add a fifth variable using this package, like for example the size or the shape of the points in the space. Here's an example of my data, and my current code:

set.seed(1)
df <- data.frame(replicate(4,sample(1:200,1000,rep=TRUE)))
addme <- data.frame(replicate(1,sample(0:1,1000,rep=TRUE)))
df <- cbind(df,addme)
colnames(df) <- c("var1","var2","var3","var4","var5")
require(rgl)
plot3d(df$var1, df$var2, df$var3, col=as.numeric(df$var4), size=0.5, type='s',xlab="var1",ylab="var2",zlab="var3")

I hope it is possible to do the 5th dimension. Many thanks,

Answer 1

Here is a ggplot2 option. I usually shy away from 3D plots as they are hard to interpret properly. I also almost never put in 5 continuous variables in the same plot as I have here...

ggplot(df, aes(x=var1, y=var2, fill=var3, color=var4, size=var5^2)) +
  geom_point(shape=21) +
  scale_color_gradient(low="red", high="green") +
  scale_size_continuous(range=c(1,12))

While this is a bit messy, you can actually reasonably read all 5 dimensions for most points.

A better approach to multi-dimensional plotting opens up if some of your variables are categorical. If all your variables are continuous, you can turn some of them to categorical with cut and then use facet_wrap or facet_grid to plot those.

For example, here I break up var3 and var4 into quintiles and use facet_grid on them. Note that I also keep the color aesthetics as well to highlight that most of the time turning a continuous variable to categorical in high dimensional plots is good enough to get the key points across (here you'll notice that the fill and border colors are pretty uniform within any given grid cell):

df$var4.cat <- cut(df$var4, quantile(df$var4, (0:5)/5), include.lowest=T)
df$var3.cat <- cut(df$var3, quantile(df$var3, (0:5)/5), include.lowest=T)

ggplot(df, aes(x=var1, y=var2, fill=var3, color=var4, size=var5^2)) +
  geom_point(shape=21) +
  scale_color_gradient(low="red", high="green") +
  scale_size_continuous(range=c(1,12)) +
  facet_grid(var3.cat ~ var4.cat)