maptools (version 1.0-1)

as.ppp: Coercion between sp objects and spatstat ppp objects

Description

Functions to convert between spatstats planar point pattern (ppp) format and sps SpatialPoints and SpatialPointsDataFrame as well as one-way conversion from SpatialGridDataFrame to ppp. S4-style as() coercion can be used as well.

Usage

as.ppp.SpatialPoints(X)
as.ppp.SpatialPointsDataFrame(X)
as.SpatialPoints.ppp(from)
as.SpatialPointsDataFrame.ppp(from)
as.SpatialGridDataFrame.ppp(from)

Arguments

from, X

object to coerce from

Methods

coerce

signature(from = "SpatialPoints", to = "ppp")

coerce

signature(from = "SpatialPointsDataFrame", to = "ppp")

coerce

signature(from = "ppp", to = "SpatialGridDataFrame")

coerce

signature(from = "ppp", to = "SpatialPointsDataFrame")

coerce

signature(from = "ppp", to = "SpatialPoints")

Warning

In spatstat all spatial objects are assumed to be planar. This means that spatstat is not designed to work directly with geographic (longitude and latitude) coordinates. If a sp object is declared to have geographic (unprojected) coordinates maptools refuses to convert directly to spatstat format. Rather, these should be projected first using e.g. spTransform. If you know what you are doing, and really want to force coercion, you can overwrite the proj4string of the sp object with NA, proj4string(x) <- CRS(NA), which will fool the system to think that the data is in local planar coordinates. This is probably not a good idea!

Details

The main conversion is between sps SpatialPoints/SpatialPointsDataFrame and spatstats ppp. Conversion between SpatialGridDataFrame and ppp should rarely be used; using as.owin.SpatialGridDataFrame is more transparent.

Examples

# NOT RUN {
run <- FALSE
if (require(spatstat, quietly=TRUE)) run <- TRUE
if (run) {
## Convert SpatialPointsDataFrame into a marked ppp
data(meuse)
coordinates(meuse) = ~x+y
meuse_ppp <- as(meuse, "ppp")
meuse_ppp # Window is the bounding rectangle
}
if (run) {
plot(meuse_ppp, which.marks = "zinc")
}
if (run) {
## Convert SpatialPoints into an unmarked ppp
meuse2 <- as(meuse, "SpatialPoints")
as(meuse2, "ppp")
}
if (run) {
## Get sampling region in grid format and assign it as observation window
data(meuse.grid)
gridded(meuse.grid) <- ~x+y
mg_owin <- as(meuse.grid, "owin")
Window(meuse_ppp) <- mg_owin
meuse_ppp # Window is now a binary image mask (TRUE/FALSE grid)
}
if (run) {
plot(meuse_ppp, which.marks = "zinc")
}
if (run) {
## Convert marked ppp back to SpatialPointsDataFrame
rev_ppp_SPDF <- as.SpatialPointsDataFrame.ppp(meuse_ppp)
summary(rev_ppp_SPDF)
}
if (run) {
## Convert marked ppp back to SpatialPoints (discarding marks)
rev_ppp_SP <- as.SpatialPoints.ppp(meuse_ppp)
summary(rev_ppp_SP)
}
if (run) {
## Convert marked ppp back to SpatialGridDataFrame (extracting the window grid)
rev_ppp_SGDF <- as.SpatialGridDataFrame.ppp(meuse_ppp)
summary(rev_ppp_SGDF)
}
# }