as.raster {grDevices} | R Documentation |
Functions to create a raster object (representing a bitmap image) and coerce other objects to a raster object.
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, ...)
x |
Any R object. |
max |
number giving the maximum of the color values range. |
... |
further arguments passed to or from other methods. |
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.
For as.raster()
, a raster object.
For is.raster()
, a logical indicating whether
x
is a raster object.
# 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)))