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https://github.com/jmlondon/projectedgridlines
https://github.com/jmlondon/projectedgridlines
Last synced: about 20 hours ago
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- Host: GitHub
- URL: https://github.com/jmlondon/projectedgridlines
- Owner: jmlondon
- Created: 2010-12-08T19:07:30.000Z (almost 14 years ago)
- Default Branch: master
- Last Pushed: 2015-01-23T21:03:34.000Z (almost 10 years ago)
- Last Synced: 2023-03-18T05:45:31.156Z (over 1 year ago)
- Language: R
- Homepage:
- Size: 459 KB
- Stars: 3
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
## Add graticules to projected maps in R
### install the package
```r
devtools::install_github('jmlondon/ProjectedGridlines', subdir = 'ProjectedGridlines')
```
### spplot example:
From [R-sig-Geo](https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20101208/ba706f4c/attachment.pl).
```r
library(ProjectedGridlines)
library(sp)
library(rgdal)
library(maptools)
library(RColorBrewer)
library(lattice)
#read in the maptools north carolina shapefile, unprojected
d <- readShapePoly(system.file("shapes/sids.shp", package="maptools")[1], proj4string=CRS("+proj=longlat +datum=NAD27"))
# create a dummy factor variable, with equal labels:
set.seed(31)
d$f = factor(sample(1:5,100,replace=T),labels=letters[1:5])
#specify a custom Albers equal centered on the coordinate data
#this works for points and polygons, but lines need to be converted to points
med.lat <- round(median(coordinates(d)[,2]))
med.lon <- round(median(coordinates(d)[,1]))
lat1<-bbox(d)[2,1]+diff(range(bbox(d)[2,]))/3
lat2<-bbox(d)[2,2]-diff(range(bbox(d)[2,]))/3
myProj <- paste("+proj=aea +lat_1=",lat1," +lat_2=",lat2," +lat_0=",med.lat,
" +lon_0=", med.lon, "+x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m",sep="")
#project the data, the graticule lines. note the gridlines function calls the unprojected data
d.proj <- spTransform(d,CRS(myProj))
#grat.lines<-spTransform(gridlines(d,ndisc=500),CRS(myProj))
g<-GetGratLines(d,myProj,list(t=0.25,b=-0.25,l=-0.25,r=0.25))
#create the sp.layout component for the graticule lines
grat.plot<-list("sp.lines",g,lwd="1.5",col="white",first=TRUE)
x_grat_at<-GetLabelCoords(g,offset=list(ew=0))$EW_Coords
y_grat_at<-GetLabelCoords(g,offset=list(ns=0))$NS_Coords
x_grat<-list(draw=TRUE,
at=x_grat_at,
labels=as.character(GetDegreeLabels(d)$EW_Labels),
tck=c(0,0),
cex=0.75)
y_grat<-list(draw=TRUE,
at=y_grat_at,
labels=as.character(GetDegreeLabels(d)$NS_Labels),
rot=90,
tck=c(0,0),
cex=0.75)
spplot(d.proj, c("f"),
panel=function(...){
panel.fill(col="gray90")
panel.polygonsplot(...)
},
sp.layout=list(grat.plot),
col.regions=brewer.pal(5, "Set3"),scales=list(x=x_grat,y=y_grat))
```
### ggplot2 example
```r
library(ProjectedGridlines)
library(sp)
library(rgdal)
library(maptools)
library(RColorBrewer)
library(ggplot2)
library(grid)
#read in the maptools north carolina shapefile, unprojected
d <- readShapePoly(system.file("shapes/sids.shp", package="maptools")[1], proj4string=CRS("+proj=longlat +datum=NAD27"))
# create a dummy factor variable, with equal labels:
set.seed(31)
d$f = factor(sample(1:5,100,replace=T),labels=letters[1:5])
#specify a custom Albers equal centered on the coordinate data
#this works for points and polygons, but lines need to be converted to points
med.lat <- round(median(coordinates(d)[,2]))
med.lon <- round(median(coordinates(d)[,1]))
lat1<-bbox(d)[2,1]+diff(range(bbox(d)[2,]))/3
lat2<-bbox(d)[2,2]-diff(range(bbox(d)[2,]))/3
myProj <- paste("+proj=aea +lat_1=",lat1," +lat_2=",lat2," +lat_0=",med.lat,
" +lon_0=", med.lon, "+x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m",sep="")
#project the data, the graticule lines. note the gridlines function calls the unprojected data
d.proj <- spTransform(d,CRS(myProj))
coordLim <- bbox(d.proj)
grat <- GetGratLines(d,myProj,list(t=0.25,b=-0.25,l=-0.25,r=0.25))
# There is no fortify method in ggplot2 for objects of class SpatialLines, which is why we create a SpatialLinesDataFrame, with dummy @data slot
gratdf <- SpatialLinesDataFrame(grat, data = data.frame(rep(NA, length(grat))), match.ID = FALSE)
## Get x, y labels and locations
x_grat_at<-GetLabelCoords(grat,offset=list(ew=0))$EW_Coords
y_grat_at<-GetLabelCoords(grat,offset=list(ns=0))$NS_Coords
x_grat<-list(draw=TRUE,
at=x_grat_at,
labels=as.character(GetDegreeLabels(d)$EW_Labels),
tck=c(0,0),
cex=0.75)
y_grat<-list(draw=TRUE,
at=y_grat_at,
labels=as.character(GetDegreeLabels(d)$NS_Labels),
rot=90,
tck=c(0,0),
cex=0.75)
# Convert spatial objects to ggplot ready dataframes
ggd.proj <- fortify(d.proj, region = "f")
ggcontour <- fortify(d.proj, region = "NAME") # Otherwise adjacent polygons containing the save factor level are merged
gggrat <- fortify(gratdf)
ggplot(ggd.proj) +
geom_polygon(aes(x=long, y=lat, group=group, fill = id)) +
geom_polygon(data = ggcontour, aes(x=long, y=lat, group=group), fill = NA, colour = 'black') +
geom_path(data = gggrat, aes(x=long,y=lat,group=group), col = 'grey', linetype = 'dashed') +
coord_equal(xlim = coordLim[1,], ylim = coordLim[2,]) +
scale_x_continuous(name = 'Lat', breaks = x_grat$at, labels = x_grat$labels) +
scale_y_continuous(name = 'Long', breaks = y_grat$at, labels = y_grat$labels) +
theme_bw() +
theme(axis.title = element_blank())
```
```r
ggplot(ggd.proj) +
geom_path(data = gggrat, aes(x=long,y=lat,group=group), col = 'white', size = 1) +
geom_polygon(aes(x=long, y=lat, group = group, fill = id)) +
geom_polygon(data = ggcontour, aes(x=long, y=lat, group=group), fill = NA, colour = 'black') +
coord_equal(xlim = coordLim[1,], ylim = coordLim[2,]) +
scale_x_continuous(name = 'Lat', breaks = x_grat$at, labels = x_grat$labels) +
scale_y_continuous(name = 'Long', breaks = y_grat$at, labels = y_grat$labels) +
theme(panel.grid = element_blank(), panel.border = element_rect(colour = "black", fill = NA), axis.title = element_blank())
```
