as.raster {grDevices}R Documentation

Create a Raster Object

Description

Functions to create a raster object (representing a bitmap image) and coerce other objects to a raster object.

Usage

is.raster(x)
as.raster(x, ...)

## S3 method for class 'logical':
as.raster(x, max=1, ...)
## S3 method for class 'numeric':
as.raster(x, max=1, ...)
## S3 method for class 'character':
as.raster(x, max=1, ...)
## S3 method for class 'matrix':
as.raster(x, max=1, ...)
## S3 method for class 'array':
as.raster(x, max=1, ...)

Arguments

x Any R object.
max number giving the maximum of the color values range.
... further arguments passed to or from other methods.

Details

It is not expected that the user will call these functions directly; functions to render bitmap images in graphics packages will make use of the as.raster() function to automatically generate a raster object from their input.

The as.raster() function is generic so methods can be written to convert other R objects to a raster object.

Value

For as.raster(), a raster object.

For is.raster(), a logical indicating whether x is a raster object.

Examples

# A red gradient
as.raster(matrix(hcl(0, 80, seq(50, 80, 10)),
                 nrow=4, ncol=5))

# Vectors are 1-column matrices ...
#   character vectors are color names ...
as.raster(hcl(0, 80, seq(50, 80, 10)))
#   numeric vectors are greyscale ...
as.raster(1:5, max=5)
#   locigal vectors are black and white ...
as.raster(1:10 %% 2 == 0)

# ... unless nrow/ncol are supplied ...
as.raster(1:10 %% 2 == 0, nrow=1)

# Matrix can also be logical or numeric ...
as.raster(matrix(c(TRUE, FALSE), nrow=3, ncol=2))
as.raster(matrix(1:3/4, nrow=3, ncol=4))

# An array can be 3-plane numeric (R, G, B planes) ...
as.raster(array(c(0:1, rep(0.5, 4)), c(2, 1, 3)))

# ... or 4-plane numeric (R, G, B, A planes)
as.raster(array(c(0:1, rep(0.5, 6)), c(2, 1, 4)))


[Package grDevices version 2.11.0 Index]