Now I have new question about this post. If the grid coordinates in DF1 are not complete, i.e. there are missing coordinates, how to fill these with -99 in the exported DF2? Thanks.
On Thu, Nov 15, 2018 at 10:57 PM David L Carlson <dcarl...@tamu.edu> wrote: > It would depend on the format of the gridded data. Assuming it is a data > frame like DF2 in my earlier answer, you just reverse the steps: > > > 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 > > > DF3 <- data.frame(as.table(as.matrix(DF2))) > Var1 Var2 Freq > 1 46 110.5 6.1 > 2 45.5 110.5 3.2 > 3 46 111 4.5 > 4 45.5 111 5.0 > 5 46 111.5 7.8 > 6 45.5 111.5 1.8 > 7 46 112 5.5 > 8 45.5 112 2.0 > > But the latitude and longitude get converted to factors and we lose the > column names: > > > DF3 <- data.frame(as.table(as.matrix(DF2))) > > colnames(DF3) <- c("latitude", "longitude", "Precip") > > DF3$latitude <- as.numeric(as.character(DF3$latitude)) > > DF3$longitude <- as.numeric(as.character(DF3$longitude)) > > ---------------------------------------- > David L Carlson > Department of Anthropology > Texas A&M University > College Station, TX 77843-4352 > > From: lily li <chocol...@gmail.com> > Sent: Tuesday, November 13, 2018 10:50 PM > To: David L Carlson <dcarl...@tamu.edu> > Cc: Sarah Goslee <sarah.gos...@gmail.com>; R mailing list < > r-help@r-project.org> > Subject: Re: [R] How to create gridded data > > 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 <mailto: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 <mailto:r-help-boun...@r-project.org> On Behalf Of Sarah > Goslee > Sent: Tuesday, November 13, 2018 8:16 AM > To: lily li <mailto:chocol...@gmail.com> > Cc: r-help <mailto: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://urldefense.proofpoint.com/v2/url?u=https-3A__www.springer.com_us_book_9781461476177&d=DwMFaQ&c=ODFT-G5SujMiGrKuoJJjVg&r=veMGHMCNZShld-KX-bIj4jRE_tP9ojUvB_Lqp0ieSdk&m=vZqNKoDe8N1TzBzeK12g2oa0cBS8VD6NDCs-hUhvt5o&s=B73PwZQrdKUmM1ML2Y5zjaEz7xqkHlzBDCrhluogK2U&e= > > and there are abundant web tutorials. > > Sarah > On Tue, Nov 13, 2018 at 2:22 AM lily li <mailto: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) > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.numberwright.com&d=DwMFaQ&c=ODFT-G5SujMiGrKuoJJjVg&r=veMGHMCNZShld-KX-bIj4jRE_tP9ojUvB_Lqp0ieSdk&m=vZqNKoDe8N1TzBzeK12g2oa0cBS8VD6NDCs-hUhvt5o&s=qSosThG59aeSFYzVFf1e-YQGbuBKVbvgVi1z9nFm884&e= > > ______________________________________________ > mailto:R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Dhelp&d=DwMFaQ&c=ODFT-G5SujMiGrKuoJJjVg&r=veMGHMCNZShld-KX-bIj4jRE_tP9ojUvB_Lqp0ieSdk&m=vZqNKoDe8N1TzBzeK12g2oa0cBS8VD6NDCs-hUhvt5o&s=2pS9yFu5bpcRyCi1vX_OEDD2Ie8ZihvOQrkDQSNu8RM&e= > PLEASE do read the posting guide > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.org_posting-2Dguide.html&d=DwMFaQ&c=ODFT-G5SujMiGrKuoJJjVg&r=veMGHMCNZShld-KX-bIj4jRE_tP9ojUvB_Lqp0ieSdk&m=vZqNKoDe8N1TzBzeK12g2oa0cBS8VD6NDCs-hUhvt5o&s=1brzEOjZ4EUr_llqwyO274DfJfsOpRBI-pmd-hp0WAQ&e= > 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.