by.im
From spatstat v1.34-1
by Adrian Baddeley
Apply Function to Image Broken Down by Factor
Splits a pixel image into sub-images and applies a function to each sub-image.
Usage
## S3 method for class 'im':
by(data, INDICES, FUN, ...)
Arguments
- data
- A pixel image (object of class
"im"
). - INDICES
- Grouping variable.
Either a tessellation (object of class
"tess"
) or a factor-valued pixel image. - FUN
- Function to be applied to each sub-image of
data
. - ...
- Extra arguments passed to
FUN
.
Details
This is a method for the generic function by
for
pixel images (class "im"
).
The pixel image data
is first divided into sub-images according
to INDICES
. Then the function FUN
is applied to each subset.
The results of each computation are returned in a list.
The grouping variable INDICES
may be either
- a tessellation (object of class
"tess"
). Each tile of the tessellation delineates a subset of the spatial domain. - a pixel image (object of class
"im"
) with factor values. The levels of the factor determine subsets of the spatial domain.
Value
- A list containing the results of each evaluation of
FUN
.
See Also
Examples
W <- square(1)
X <- as.im(function(x,y){sqrt(x^2+y^2)}, W)
Y <- dirichlet(runifpoint(12, W))
# mean pixel value in each subset
unlist(by(X, Y, mean))
# trimmed mean
unlist(by(X, Y, mean, trim=0.05))
Community examples
Looks like there are no examples yet.