ipairs {IDPmisc}R Documentation

Image Scatter Plot Matrix for Large Datasets

Description

Produces an image scatter plot matrix of large datasets where the colors encode the density of the points in the scatter plots.

Usage

ipairs(x,
       pixs = 1, zmax = NULL, ztransf=function(x){x},
       colramp = IDPcolorRamp, border = FALSE, 
       labels, cex.lab = NULL, nlab = 5, minL.lab = 2, pty = "s", 
       main = NULL, cex.main = par("cex.main"), verbose = FALSE, ...)

Arguments

x data.frame or matrix
pixs Pixel size in mm on the plotting device.
zmax Maximum number ofcounts per pixel in the plot. When NULL, each scatter plot has its individual scale. If a number >= maximum number of counts per pixel is supplied, the scale will be identical for all scatter plots. The maximum number of counts per pixel is delivered by the return value.
ztransf Function to transform the counts per pixel, which will be mapped by the function in colramp to well defined colors. The user has to make sure that the transformed counts lie in the range [0,zmax], where zmax is any positive number (>=2).
colramp Color ramp to encode the number of counts within a pixel.
border Shall border be drawn between the colors in the legend: TRUE / FALSE.
labels Labels of columns. If NULL the names of x are used.
minL.lab The minimum length of the abbreviations of factor levels, used to label the axes.
cex.lab Size of the labels. If NULL they are calculated automatically.
nlab Approximate number of labels on axes.
pty See Argument pty in par.
main Titel.
cex.main Size of title.
verbose When verbose == TRUE, the values for cex.main and cex.lab are returned in addition to zmax.
... Additional arguments to plot.default

Details

The idea is similar to plot.hexbin. The hexagons are better suited to reflect the density of points in a plane than the squares used here. Nevertheless squares are, contrary to hexagons, invariant to reflexions at the x- and y-axis and therefore suited for scatter plot matrices and also for plotting factors.

The code is based on R function pairs V1.7.

Value

Maximum number of counts per Pixel found. Additional elements are returned when verbose == TRUE.

Note

When you get the error message "Zmax too small! Densiest aereas are out of range!" you must run the function again without specifying zmax. The value returned gives you the minimum value allowed for zmax.

Author(s)

Andreas Ruckstuhl, Rene Locher

See Also

ilagplot, ixyplot, Image

Examples

zmax <- ipairs(airquality,pixs=2,main="Air Quality")
ipairs(airquality,pixs=2,zmax=zmax,border=TRUE)

## example with factors
zmax <- ipairs(iris,pixs=2)
ipairs(iris,pixs=2,zmax=zmax)

## a really huge dataset
if(require(SwissAir)) {
  data(AirQual)

  ## low correlation
  ipairs(AirQual[,c("ad.O3","lu.O3","sz.O3")],
         ztransf=function(x){x[x<1] <- 1; log2(x)*10})
  
  ipairs(AirQual[,c("ad.NO","lu.NO","sz.NO")],
         ztransf=function(x){x[x<1] <- 1; log2(x)*10})

  ## high correlation
  Ox <- AirQual[,c("ad.O3","lu.O3","sz.O3")]+
    AirQual[,c("ad.NOx","lu.NOx","sz.NOx")]-
      AirQual[,c("ad.NO","lu.NO","sz.NO")]
  names(Ox) <- c("ad","lu","sz")
  ipairs(Ox,cex.lab=2, ztransf=function(x){x[x<1] <- 1; log2(x)*10})

  ## cf. ?AirQual for the explanation of the physical and
  ## chemical background
} else print("Package SwissAir is not available")


[Package IDPmisc version 0.9.9 Index]