gpar {grid}R Documentation

Function to produce a Graphical Parameter Object

Description

This function returns an object of class "gpar". This is basically a list of name-value pairs.

Usage

gpar(...)

Arguments

... Any number of named arguments.

Details

All grid viewports and (predefined) graphical objects have a slot called gp, which contains a "gpar" object. When a viewport is pushed onto the viewport stack and when a graphical object is drawn, the settings in the "gpar" object are enforced. In this way, the graphical output is modified by the gp settings until the graphical object has finished drawing, or until the viewport is popped off the viewport stack, or until some other viewport or graphical object is pushed or begins drawing.

Valid parameter names are:
col Colour for lines and borders.
fill Colour for filling rectangles, polygons, ...
lty Line type
lwd Line width
fontsize The size of text (in points)
fontfamily The font family
fontface The font face (bold, italic, ...)
lineheight The height of a line as a multiple of fontsize
font Font face (alias for fontface; for backward compatibility)

For most devices, the fontfamily is specified when the device is first opened and may not be changed thereafter – i.e., specifying a different font family via fontfamily will be ignored. This will hopefully change in future versions of R. Also, there is an important exception: fontfamily may be used to specify one of the Hershey Font families (e.g., HersheySerif) and this specification will be honoured on all devices.

The specification of fontface follows the R base graphics standard: 1 = plain, 2 = bold, 3 = italic, 4 = bold italic.

Specifying the value NULL for a parameter is the same as not specifying any value for that parameter, except for col and fill, where NULL indicates not to draw a border or not to fill an area (respectively).

All parameter values can be vectors of multiple values. (This will not always make sense – for example, viewports will only take notice of the first parameter value.)

Value

An object of class "gpar".

Author(s)

Paul Murrell

See Also

Hershey.

Examples

gpar(col="red")
gpar(col="blue", lty="solid", lwd=3, fontsize=16)
grid.newpage()
vp <- viewport(w=.8, h=.8, gp=gpar(col="blue"))
grid.collection(grid.rect(gp=gpar(col="red"), draw=FALSE),
                grid.text("The rect is its own colour (red)\nbut this text is the colour\nset by the collection (green)", draw=FALSE),
                gp=gpar(col="green"), vp=vp)
grid.text("This text is the colour set by the viewport (blue)",
          y=1, just=c("center", "bottom"), gp=gpar(fontsize=20), vp=vp)
grid.newpage()
# example with multiple values for a parameter
grid.points(1:10/11, 1:10/11, gp=gpar(col=1:10))

[Package Contents]