im.apply | R Documentation |
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"
).
.
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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