imcov {spatstat} | R Documentation |
Computes the unnormalised spatial covariance function of a pixel image.
imcov(X, Y=X)
X |
A pixel image (object of class |
Y |
Optional. Another pixel image. |
The (uncentred, unnormalised) spatial covariance function of a pixel image X in the plane is the function C(v) defined for each vector v as the integral
C(u) = integral of X(u) * X(u+v) du
over all spatial locations u, where X(u) denotes the pixel value at location u.
This command computes a discretised approximation to
the spatial covariance function, using the Fast Fourier Transform.
The return value is
another pixel image (object of class "im"
) whose greyscale values
are values of the spatial covariance function.
If the argument Y
is present, then imcov(X,Y)
computes the set cross-covariance function C(u)
defined as
C(u) = integral of X(u) * Y(u+v) du.
A pixel image (an object of class "im"
) representing the
spatial covariance function of X
,
or the cross-covariance of X
and Y
.
Adrian Baddeley Adrian.Baddeley@csiro.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner r.turner@auckland.ac.nz
setcov
,
owin
,
as.owin
,
erosion
w <- owin(c(0,1),c(0,1)) X <- as.im(w) v <- imcov(X) plot(v)