iplot {IDPmisc}

Image Scatter Plot for Large Datasets

Description

Produces an image scatter plot of large datasets where the colors encode the density of the points in the scatter plot. Works also with factors.

Usage

iplot(x, y = NULL,
      pixs = 1, zmax = NULL, ztransf = function(x){x},
      colramp = IDPcolorRamp, cex = par("cex"),
      main = NULL, d.main = 1, cex.main = par("cex.main"),
      xlab = NULL, ylab = NULL, cex.lab = 1,
      legend = TRUE, d.legend = 1,
      cex.axis = par("cex.axis"), nlab.xaxis = 5, nlab.yaxis = 5,
      minL.axis = 3, las = 1, border = FALSE,
      oma = c(5,4,1,0)+0.1, mgp = c(2,0.5,0)*cex.axis, tcl = -0.3, ...
      )

Arguments

x, y

Coordinates of points whose density is to be plotted. If x ist a matrix or a data.frame, the first two column are used as x and y respectively. y must be in this case NULL. x and y may be numeric or factor variable.

pixs

Pixelsize in mm.

zmax

Maximum number of counts per pixel in the plot. When NULL, the density in the scatter plot is encoded from 0 to maximum number of counts per pixel observed. zmax must be equal or larger than maximum number of counts found. The maximum number of counts per pixel is delivered by the return value.

ztransf

Function to transform the number of 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 density lies in the range [0,zmax], where zmax is any positive number (>=2). For examples see ipairs and ilagplot.

colramp

Color ramp to encode the number of counts within a pixel.

cex

Magnification of text relative to default.

main

Title.

d.main

Vertical distance between upper border of scatter plots and the title line in multiples of title height.

cex.main

Magnification used for title relative to the current setting of cex.

xlab

Label for x-axis.

ylab

Label for y-axis.

cex.lab

Magnification used for text in axis labels relative to the current setting of cex

legend

Logical. When FALSE, no legend is plotted and space is saved in figure region.

d.legend

Horizontal distance between right border of scatter plot and legend in multiples of title height.

cex.axis

Magnification used for axis annotation relative to the current setting of cex.

nlab.xaxis, nlab.yaxis

Approximate number of labels on x- and y-axes respectively.

minL.axis

The minimum length of the abbreviations of factor levels, used to label the axes ticks.

las

Orientation of labels on axes.

border

Logical. When TRUE, a border is drawn around the individual colors in the legend.

oma

Outer margin. Cf. par

mgp, tcl

Cf. par

...

Additional arguments to par

Details

The idea of this plot is similar to gplot.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.

Value

Maximum number of counts per Pixel found.

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, ipairs, Image

Examples

x <-  rnorm(10000)
y <- atan(rnorm(10000, 0))
iplot(x, y)
iplot(x, pixs = 2)

oma <- c(5,5,0,0)
iplot(iris[,1:2], pixs = 4, oma = oma)
iplot(iris[,"Petal.Width"], iris[,"Species"], pixs = 4, oma = oma)
iplot(x = iris[,"Species"], y = iris[,"Petal.Width"], pixs = 10,border = TRUE,
        xlab = "Species",
        ylab = "Petal Width",
        main = "Iris Species and Petal Width", oma = oma)

iplot(iris$Species, iris$Petal.Width,pixs = 3, minL.axis = 10,
      oma = c(3,6,0,0), mgp = c(4, 1, 0),
      cex.axis = 2, cex.lab = 2, cex.main = 2, main = "Larger fonts")