smoothScatter {graphics} | R Documentation |
smoothScatter
produces a smoothed color density
representation of a scatterplot, obtained through a (2D) kernel
density estimate.
smoothScatter(x, y = NULL, nbin = 128, bandwidth,
colramp = colorRampPalette(c("white", blues9)),
nrpoints = 100, ret.selection = FALSE,
pch = ".", cex = 1, col = "black",
transformation = function(x) x^.25,
postPlotHook = box,
xlab = NULL, ylab = NULL, xlim, ylim,
xaxs = par("xaxs"), yaxs = par("yaxs"), ...)
x, y |
the |
nbin |
numeric vector of length one (for both directions) or two
(for x and y separately) specifying the number of equally spaced
grid points for the density estimation; directly used as
|
bandwidth |
numeric vector (length 1 or 2) of smoothing bandwidth(s).
If missing, a more or less useful default is used. |
colramp |
function accepting an integer |
nrpoints |
number of points to be superimposed on the density
image. The first |
ret.selection |
|
pch, cex, col |
arguments passed to |
transformation |
function mapping the density scale to the color scale. |
postPlotHook |
either |
xlab, ylab |
character strings to be used as axis labels, passed
to |
xlim, ylim |
numeric vectors of length 2 specifying axis limits. |
xaxs, yaxs, ... |
further arguments passed to |
smoothScatter
produces a smoothed version of a scatter plot.
Two dimensional (kernel density) smoothing is performed by
bkde2D
from package KernSmooth.
See the examples for how to use this function together with
pairs
.
If ret.selection
is true, a vector of integers of length
nrpoints
(or smaller, if there are less finite points inside
xlim
and ylim
) with the indices of the low-density
points drawn, ordered with lowest density first.
Florian Hahne at FHCRC, originally
bkde2D
from package KernSmooth;
densCols
which uses the same smoothing computations and
blues9
in package grDevices.
scatter.smooth
adds a loess
regression smoother to a scatter plot.
## A largish data set
n <- 10000
x1 <- matrix(rnorm(n), ncol = 2)
x2 <- matrix(rnorm(n, mean = 3, sd = 1.5), ncol = 2)
x <- rbind(x1, x2)
oldpar <- par(mfrow = c(2, 2), mar=.1+c(3,3,1,1), mgp = c(1.5, 0.5, 0))
smoothScatter(x, nrpoints = 0)
smoothScatter(x)
## a different color scheme:
Lab.palette <- colorRampPalette(c("blue", "orange", "red"), space = "Lab")
i.s <- smoothScatter(x, colramp = Lab.palette,
## pch=NA: do not draw them
nrpoints = 250, ret.selection=TRUE)
## label the 20 very lowest-density points,the "outliers" (with obs.number):
i.20 <- i.s[1:20]
text(x[i.20,], labels = i.20, cex= 0.75)
## somewhat similar, using identical smoothing computations,
## but considerably *less* efficient for really large data:
plot(x, col = densCols(x), pch = 20)
## use with pairs:
par(mfrow = c(1, 1))
y <- matrix(rnorm(40000), ncol = 4) + 3*rnorm(10000)
y[, c(2,4)] <- -y[, c(2,4)]
pairs(y, panel = function(...) smoothScatter(..., nrpoints = 0, add = TRUE),
gap = 0.2)
par(oldpar)