Apply Function Pixelwise to List of Images
Returns a pixel image obtained by applying a function to the values of corresponding pixels in several pixel images.
im.apply(X, FUN, ..., fun.handles.na=FALSE, check=TRUE)
X |
A list of pixel images (objects of class |
FUN |
A function that can be applied to vectors, or a character string giving the name of such a function. |
... |
Additional arguments to |
fun.handles.na |
Logical value specifying what to do when the data include
|
check |
Logical value specifying whether to check that the images in
|
The argument X should be a list of pixel images
(objects of class "im"). If the images do not have
identical pixel grids, they will be converted to a common
grid using harmonise.im.
At each pixel location, the values of the images in X
at that pixel will be extracted as a vector. The function
FUN will be applied to this vector. The result (which should be
a single value) becomes the pixel value of the resulting image.
The argument fun.handles.na specifies what to do
when some of the pixel values are NA.
If fun.handles.na=FALSE (the default),
the function FUN is never applied to data that include
NA values; the result is defined to be NA whenever
the data contain NA.
If fun.handles.na=TRUE, the function FUN will be applied to
all pixel data, including those which contain NA values.
A pixel image (object of class "im").
Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.
eval.im for algebraic operations with images.
# list of two pixel images Y <- solapply(bei.extra, scaletointerval) plot(Y) im.apply(Y, max) im.apply(Y, sum) ## Example with incompatible patterns of NA values B <- owin(c(438, 666), c(80, 310)) Y[[1]][B] <- NA opa <- par(mfrow=c(2,2)) plot(Y[[1]]) plot(Y[[2]]) #' Default action: NA -> NA plot(im.apply(Y, mean)) #' Use NA handling in mean.default plot(im.apply(Y, mean, na.rm=TRUE, fun.handles.na=TRUE)) par(opa)
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