IDPmisc (version 0.9.3)

ipairs: 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

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 positiv

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

Value

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

concept

• large dataset
• huge dataset

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.

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")