Thanks, Sarah's answer helps the question. Now how to change the gridded data back to DF1 format? I don't know how to name the format, thanks.
On Tue, Nov 13, 2018 at 10:56 PM David L Carlson <dcarl...@tamu.edu> wrote: > Sarah's answer is probably better depending on what you want to do with > the resulting data, but here's a way to go from your original DF1 to DF2: > > > DF1 <- structure(list(latitude = c(45.5, 45.5, 45.5, 45.5, 46, 46, 46, > + 46), longitude = c(110.5, 111, 111.5, 112, 110.5, 111, 111.5, > + 112), Precip = c(3.2, 5, 1.8, 2, 6.1, 4.5, 7.8, 5.5)), > + class = "data.frame", row.names = c(NA, -8L)) > > > # Convert to table with xtabs() > > DF2 <- xtabs(Precip~latitude+longitude, DF1) > > > > # Reverse the order of the latitudes > > DF2 <- DF2[rev(rownames(DF2)), ] > > DF2 > longitude > latitude 110.5 111 111.5 112 > 46 6.1 4.5 7.8 5.5 > 45.5 3.2 5.0 1.8 2.0 > > # Convert to a data frame > > DF2 <- as.data.frame.matrix(DF2) > > DF2 > 110.5 111 111.5 112 > 46 6.1 4.5 7.8 5.5 > 45.5 3.2 5.0 1.8 2.0 > > ---------------------------------------- > David L Carlson > Department of Anthropology > Texas A&M University > College Station, TX 77843-4352 > > > -----Original Message----- > From: R-help <r-help-boun...@r-project.org> On Behalf Of Sarah Goslee > Sent: Tuesday, November 13, 2018 8:16 AM > To: lily li <chocol...@gmail.com> > Cc: r-help <r-help@r-project.org> > Subject: Re: [R] How to create gridded data > > If you want an actual spatial dataset, the best place to ask is R-sig-geo > > R has substantial capabilities for dealing with gridded spatial data, > including in the sp, raster, and sf packages. > > Here's one approach, creating a SpatialGridDataFrame, which can be > exported in any standard raster format using the rgdal package. > > DF2 <- DF1 > coordinates(DF2) <- ~longitude + latitude > gridded(DF2) <- TRUE > fullgrid(DF2) <- TRUE > > I recommend Roger Bivand's excellent book: > https://www.springer.com/us/book/9781461476177 > > and there are abundant web tutorials. > > Sarah > On Tue, Nov 13, 2018 at 2:22 AM lily li <chocol...@gmail.com> wrote: > > > > Hi R users, > > > > I have a question about manipulating data. For example, I have DF1 as the > > following, how to transform it to a gridded dataset DF2? In DF2, each > value > > Precip is an attribute of the corresponding grid cell. So DF2 is like a > > spatial surface, and can be imported to ArcGIS. Thanks for your help. > > > > DF1 > > latitude longitude Precip > > 45.5 110.5 3.2 > > 45.5 111 5.0 > > 45.5 111.5 1.8 > > 45.5 112 2.0 > > 46 110.5 6.1 > > 46 111 4.5 > > 46 111.5 7.8 > > 46 112 5.5 > > ... > > > > > > DF2 > > 6.1 4.5 7.8 5.5 > > 3.2 5.0 1.8 2.0 > > ... > > > > > -- > Sarah Goslee (she/her) > http://www.numberwright.com > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
