Dear all,I want to calculate a grid of time spent per cell with albatross data. The goal is then to relate this to fisheries data set on a 1x1° grid. I use the trip package with tripGrid(), but have some problems with birds crossing the date line. Usually I use a projection to do that but here I need to keep the 1x1° grid in order to relate density tu some data (fisheries...).
I've tried with recenter() and nowrapSpatialLines(), without success. Here a code:
library(trip) library(maps) # to draw world mapsd <- data.frame(x=c(seq(50, 180, 10), seq(-170, 50, 10)), y=rnorm(n=37, m=-50, sd=3), tms=Sys.time()-(37:1*60*60*24), id=rep(1, 37)) # an example
coordinates(d) <- ~x+y
tr <- trip(d, c("tms", "id"))
proj4string(at) <- CRS("+proj=longlat +ellps=WGS84")
map('world')
plot(tr, add=T)
points(coordinates(tr), t="l")
# grid
grid.base <- expand.grid(Long=seq(-180, 180, by=1), Lat=seq(-70, -15,
by=1)) # tab coords
coordinates(grid.base) <- ~ Long + Lat
proj4string(grid.base) <- CRS("+proj=longlat +ellps=WGS84")
gt <- makeGridTopology(grid.base, cellsize = c(1, 1)) # def grid topo
# time spent per cell
tppc <- tripGrid(tr, grid = gt)
tppc01 <- tppc # a copy for pres/abs
tpp...@data$z <- ifelse(t...@data$z > 0, 1, 0)
image(tppc, col=rev(heat.colors(500))) # seems ok
map('world', add=T)
points(coordinates(tr), t="l")
# but with presence/absence:
image(tppc01, col=c("white", "green"))
map('world', add=T)
points(coordinates(tr), t="l", col="blue")
Some ideas ?
Many thanks for your time.
David
--
***************************************************
David PINAUD
Ingénieur de Recherche "Analyses spatiales"
Centre d'Etudes Biologiques de Chizé - CNRS UPR1934
79360 Villiers-en-Bois, France
poste 485
Tel: +33 (0)5.49.09.35.58 Fax: +33 (0)5.49.09.65.26 http://www.cebc.cnrs.fr/ *************************************************** __________ Information from ESET Mail Security, version of virus signature database 5346 (20100806) __________ The message was checked by ESET Mail Security. http://www.eset.com
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