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)