swiss_role.R

# Swiss roll and Sleepwalk

n <- 10000

# Draw random position on a rectangle
x0 <- runif( n, 0, 2*pi )
y0 <- runif( n, 0, 6*pi )

# Roll up the rectangle to form a Swiss roll
x <- x0 + rnorm( n, 0, .3 )
y <- y0 * cos( y0 ) + rnorm( n, 0, .3 )
z <- y0 * sin( y0 ) + rnorm( n, 0, .3 )

# Plot an x-z cut to show the roll's cross section
plot( y, z, asp=1, col=rje::cubeHelix(n*1.2)[rank(y0)] )

# Calculate a dimension-reduced embedding
ump <- uwot::umap( cbind( x, y, z ) )

# Plot the UMAP embedding
plot(ump, asp=1, col=rje::cubeHelix(n*1.2)[rank(y0)] )

# Visualize the embedding with Sleepwalk
sleepwalk::sleepwalk( ump, cbind( x, y, z ) )