Hi
To read netcdf data (or any other "gridded" spatial time data) I find it
convenient to define new classes Spatial3dArray and Spatial4dArray.
setClass("Spatial3dArray",
representation("Spatial", data = "array", coords = "list",
time = "character", btime = "character"),
prototype= list(data = array(NA, c(1,1,1,1)),
bbox=matrix(NA),
proj4string = CRS(as.character(NA)),
coords = list(1,1),
time = "posix",
btime = "posix"))
##########################################
###################EXAMPLE##################
##########################################
x <- matrix(seq(-10, 10, length = 100), 100, 100,
byrow = FALSE)
y <- matrix(seq(-10, 10, length = 100), 100, 100,
byrow = TRUE)
tm <- 1:10
tm.c <- as.character(seq(as.POSIXct("2002-01-01 06:00:00",
"2002-01-01 15:00:00"),
by="hours",
length.out=10))
z <- array(NA, c(dim(x)[1], dim(x)[2], length(tm.c), 1))
for (i in 1:10) {
z[,,i,] <- i * ( sin(sqrt(x^2+y^2)))
}
sin3dA <- new("Spatial3dArray",
data = z,
coords = list(x, y),
bbox = matrix(c(min(x), min(y), max(x), max(y), 2, 2), 2, 2,
dimnames = list(NULL, c("min","max"))),
time = tm.c,
btime = c(min(tm.c), max(tm.c)))
dimnames(slot(sin3dA, "data")) = list(NULL,
NULL,
slot(sin3dA, "time"),
c("a"))
names(slot(sin3dA, "coords")) <- c("x", "y")
##########################################
for the coordinates method I would like to have two options on how to return
the coordinates; "list" or default "sp":
coordinates.3dArray <- function (obj, type = "sp") {
lat <- slot(obj, "coords")[[1]]
long <- slot(obj, "coords")[[2]]
if (type == "list") {
return(list(long=long, lat=lat))
} else if (type == "sp") {
res <- as.matrix(cbind(c(long), c(lat)))
dimnames(res) <- list(NULL, c("x1", "x2"))
}
}
setMethod("coordinates", signature("Spatial3dArray"), coordinates.3dArray)
This means that the default coordinates method in sp has to include the option
"..." . Would it be possible to include this in a future release of sp?
The reason I want to keep the list option is to use a matrix oriented approach
in spplot, overlay, etc. methods. I also feel having a matrix/array approach
with these kind of data makes sense. Allowing type = "sp" means overlay() will
work more or less out of the box (however I would like to return a matrix),
and still I could get the list/matrix when desired.
Best wishes
Torleif Markussen Lunde
Centre for International Health
Bjerknes Centre for Climate Research
University of Bergen
Norway
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