graticule.R
In graticule: Meridional and Parallel Lines for Maps

## ---- echo = FALSE------------------------------------------------------------
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.path = "README-"
)



## ----message=FALSE, eval=FALSE------------------------------------------------
#  library(raster)
#  
#  library(graticule)
#  
#  ## VicGrid
#  prj <- "+proj=lcc +lat_1=-36 +lat_2=-38 +lat_0=-37 +lon_0=145 +x_0=2500000 +y_0=2500000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"
#  
#  
#  ## specify exactly where we want meridians and parallels
#  lons <- seq(140, 150, length = 5)
#  lats <- seq(-40, -35, length = 6)
#  ## optionally, specify the extents of the meridians and parallels
#  ## here we push them out a little on each side
#  xl <-  range(lons) + c(-0.4, 0.4)
#  yl <- range(lats) + c(-0.4, 0.4)
#  ## build the lines with our precise locations and ranges
#  grat <- graticule(lons, lats, proj = prj, xlim = xl, ylim = yl)
#  ## build the labels, here they sit exactly on the western and northern extent
#  ## of our line ranges
#  labs <- graticule_labels(lons, lats, xline = min(xl), yline = max(yl), proj = prj)
#  
#  ## set up a map extent and plot
#  op <- par(mar = rep(0, 4))
#  plot(extent(grat) + c(4, 2) * 1e5, asp = 1, type = "n", axes = FALSE, xlab = "", ylab = "")
#  #plot(pmap, add = TRUE)
#  ## the lines are a SpatialLinesDataFrame
#  plot(grat, add = TRUE, lty = 5, col = rgb(0, 0, 0, 0.8))
#  ## the labels are a SpatialPointsDataFrame, and islon tells us which kind
#  text(subset(labs, labs$islon), lab = parse(text = labs$lab[labs$islon]), pos = 3)
#  text(subset(labs, !labs$islon), lab = parse(text = labs$lab[!labs$islon]), pos = 2)
#  par(op)
#  

## ----message=FALSE------------------------------------------------------------
library(raster)
library(graticule)

tfile <- system.file("extdata",  "nt_20140320_f17_v01_s.bin", package = "graticule")
ice <- raster(tfile)

meridians <- seq(-180, 160, by = 20)
parallels <- c(-80, -73.77, -68, -55, -45)
mlim <- c(-180, 180)
plim <- c(-88, -50)
grat <- graticule(lons = meridians, lats = parallels, xlim = mlim, ylim = plim, proj = projection(ice))
labs <- graticule_labels(meridians, parallels, xline = -45, yline = -60, proj = projection(ice))
plot(ice, axes = FALSE)
plot(grat, add = TRUE, lty = 3)
text(labs, lab = parse(text= labs$lab), col= c("firebrick", "darkblue")[labs$islon + 1], cex = 0.85)
title(sprintf("Sea ice concentration %s", gsub(".bin", "", basename(tfile))), cex.main = 0.8)
title(sub = projection(ice), cex.sub = 0.6)

## -----------------------------------------------------------------------------
polargrid <- graticule(lons = c(meridians, 180), lats = parallels,  proj = projection(ice), tiles = TRUE)
centroids <- reproj::reproj_xy(coordinates(polargrid), "+proj=longlat +datum=WGS84", source = projection(ice))
labs <- graticule_labels(meridians, parallels,  proj = projection(ice))
#labs <- graticule_labels(as.integer(centroids[,1]), as.integer(centroids[,2]),  proj = projection(ice))
#labs <- labs[!duplicated(as.data.frame(labs)), ] ## this needs a fix
cols <- sample(colors(), nrow(polargrid))
op <- par(mar = rep(0, 4))
plot(polargrid, col  = cols, bg = "black")
text(labs[labs$islon, ], lab = parse(text = labs$lab[labs$islon]), col = "white",  cex = 0.9, pos = 3)
par(op)


## -----------------------------------------------------------------------------
devtools::session_info()