| as.im {spatstat} | R Documentation |
Converts various kinds of data to a pixel image
as.im(X, W=as.mask(as.owin(X), dimyx=dimyx), ..., dimyx=NULL)
X |
Data to be converted to a pixel image. |
W |
Window object which determines the spatial domain of the image |
... |
Additional arguments passed to X when X
is a function. |
dimyx |
Optional. Dimensions for the pixel array.
An integer, or vector of 2 integers c(ny, nx).
|
This function converts the data X into a pixel image
object of class "im" (see im.object).
Currently X may be any of the following:
"im".
"owin" (see
owin.object). The result is an image
with all pixel entries equal to 1 inside the window X,
and NA outside.
W (and NA outside).
Argument W is required.
function(x, y, ...)
which is to be evaluated to yield the image pixel values.
In this case, the additional argument W must be present.
This window will be converted to
a binary image mask. Then the function X will be evaluated
in the form X(x, y, ...) where x and y are
vectors containing the x and y coordinates
of all the pixels in the image mask, and ... are any extra
arguments given. This function must return a
vector or factor of the same length as the input vectors,
giving the pixel values.
x, y, z in the format expected by
the standard R functions
image.default and contour.default.
That is, z is a matrix of pixel values, x and y
are vectors of x and y coordinates respectively,
and z[i,j] is the pixel value for the location
(x[i],y[j]).
The spatial domain (enclosing rectangle) of the pixel image
is determined by the argument W. If W is absent,
the spatial domain is determined by X.
When X is a function or a single numerical value,
W is required.
The pixel array dimensions of the final resulting image are determined by (in priority order)
dimyx if present;
W, if it is
present and if it is a binary mask;
X if it is an image,
a binary mask, or a list(x,y,z);
spatstat.options.
Note that if dimyx is given, this will override
the pixel dimensions of X if it has them.
Thus, as.im can be used to change an image's pixel dimensions.
An image object of class "im".
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
data(demopat)
# window object
W <- demopat$window
plot(W)
Z <- as.im(W)
image(Z)
# function
Z <- as.im(function(x,y) {x^2 + y^2}, unit.square())
image(Z)
# function with extra arguments
f <- function(x, y, x0, y0) {
sqrt((x - x0)^2 + (y-y0)^2)
}
Z <- as.im(f, unit.square(), x0=0.5, y0=0.5)
image(Z)
# Revisit the Sixties
data(letterR)
Z <- as.im(f, letterR, x0=2.5, y0=2)
image(Z)
# usual convention in S
stuff <- list(x=1:10, y=1:10, z=matrix(1:100, nrow=10))
Z <- as.im(stuff)
# convert to finer grid
Z <- as.im(Z, dimyx=256)