grid.function Draw a curve representing a function

Description

Draw a curve representing a function.

Usage

grid.function(...)
functionGrob(f, n = 101, range = "x", units = "native",
             name = NULL, gp=gpar(), vp = NULL)

grid.abline(intercept, slope, ...)

Arguments

f	A function that must take a single argument and return a list with two numeric components named x and y.
n	The number values that will be generated as input to the function f.
range	Either "x", "y", or a numeric vector. See the ‘Details’ section.
units	A string indicating the units to use for the x and y values generated by the function.
intercept	Numeric.
slope	Numeric.
...	Arguments passed to grid.function()
name	A character identifier.
gp	An object of class "gpar", typically the output from a call to the function gpar. This is basically a list of graphical parameter settings.
vp	A Grid viewport object (or NULL).

Details

n values are generated and passed to the function f and a series of lines are drawn through the resulting x and y values.

The generation of the n values depends on the value of range. In the default case, dim is "x", which means that a set of x values are generated covering the range of the current viewport scale in the x-dimension. If dim is "y" then values are generated from the current y-scale instead. If range is a numeric vector, then values are generated from that range.

grid.abline() provides a simple front-end for a straight line parameterized by intercept and slope.

Value

A functiongrob grob.

Author(s)

Paul Murrell

See Also

Grid, viewport

Examples

    # abline
    # NOTE: in ROOT viewport on screen, (0, 0) at top-left
    #       and "native" is pixels!
    grid.function(function(x) list(x=x, y=0 + 1*x))
    # a more "normal" viewport with default normalized "native" coords
    grid.newpage()
    pushViewport(viewport())
    grid.function(function(x) list(x=x, y=0 + 1*x))
    # slightly simpler
    grid.newpage()
    pushViewport(viewport())
    grid.abline()
    # sine curve
    grid.newpage()
    pushViewport(viewport(xscale=c(0, 2*pi), yscale=c(-1, 1)))
    grid.function(function(x) list(x=x, y=sin(x)))
    # constrained sine curve
    grid.newpage()
    pushViewport(viewport(xscale=c(0, 2*pi), yscale=c(-1, 1)))
    grid.function(function(x) list(x=x, y=sin(x)),
                  range=0:1)
    # inverse sine curve
    grid.newpage()
    pushViewport(viewport(xscale=c(-1, 1), yscale=c(0, 2*pi)))
    grid.function(function(y) list(x=sin(y), y=y),
                  range="y")
    # parametric function
    grid.newpage()
    pushViewport(viewport(xscale=c(-1, 1), yscale=c(-1, 1)))
    grid.function(function(t) list(x=cos(t), y=sin(t)),
                  range=c(0, 9*pi/5))
    # physical abline
    grid.newpage()
    grid.function(function(x) list(x=x, y=0 + 1*x),
                  units="in")