Sorry to have missed this. There's really no way to do this in longitude / latitude without a lot of manual handling. You could split into two trips, one using the eastern hemisphere, the other the western and use a shared [-180,180] grid that you sum together.
What to do at the split coordinate depends on your actual data, there are many options. If you are still looking for an answer I could have a closer look at your example code, but real data would be more helpful if you can share it. There are a number of problems in the code you posted that prevent it from being easily run. Cheers, Mike. On Fri, Aug 6, 2010 at 8:10 PM, Pinaud David <pin...@cebc.cnrs.fr> wrote: > 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 maps > > d <- 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 > > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > -- Michael Sumner Institute for Marine and Antarctic Studies, University of Tasmania Hobart, Australia e-mail: mdsum...@gmail.com _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology