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

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)))