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Quick approximation for map projections #922

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Mar 25, 2014
Merged

Quick approximation for map projections #922

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7637548
Quick approximation for map projections
jiho Apr 29, 2013
4f6373c
Fix bug in documentation
jiho Feb 27, 2014
f64ed7e
Fix coding style and spelling for new coord_quickmap
jiho Mar 17, 2014
f0b42e9
Add NEWS bit for coord_quickmap
jiho Mar 17, 2014
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Fix coding style and spelling for new coord_quickmap
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@jiho
jiho committed Mar 17, 2014
commit f64ed7e3687efa0361b1b0aaa51f83058f591b91
10 changes: 5 additions & 5 deletions R/coord-quickmap.R
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#' Cartesian coordinates with an aspect ratio approximating mercator projection.
#' Cartesian coordinates with an aspect ratio approximating Mercator projection.
#'
#' The represenation of a portion of the earth, wich is approximately spherical,
#' onto a flat 2D plane requires a projection. This is what
Expand Down Expand Up @@ -26,8 +26,8 @@
#' # Create a lat-long dataframe from the maps package
#' nz <- map_data("nz")
#' # Prepare a plot of the map
#' nzmap <- ggplot(nz, aes(x=long, y=lat, group=group)) +
#' geom_polygon(fill="white", colour="black")
#' nzmap <- ggplot(nz, aes(x = long, y = lat, group = group)) +
#' geom_polygon(fill = "white", colour = "black")
#'
#' # Plot it in cartesian coordinates
#' nzmap
Expand All @@ -51,8 +51,8 @@ coord_aspect.quickmap <- function(coord, ranges) {

# compute distance corresponding to 1 degree in either direction
# from the center
x.dist <- dist_central_angle(x.center+c(-0.5,0.5), rep(y.center,2))
y.dist <- dist_central_angle(rep(x.center,2), y.center+c(-0.5,0.5))
x.dist <- dist_central_angle(x.center + c(-0.5, 0.5), rep(y.center, 2))
y.dist <- dist_central_angle(rep(x.center, 2), y.center+c(-0.5, 0.5))
# NB: this makes the projection correct in the center of the plot and
# increasingly less correct towards the edges. For regions of reasonnable
# size, this seems to give better results than computing this ratio from
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6 changes: 3 additions & 3 deletions man/coord_quickmap.Rd
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
% Generated by roxygen2 (4.0.0): do not edit by hand
\name{coord_quickmap}
\alias{coord_quickmap}
\title{Cartesian coordinates with an aspect ratio approximating mercator projection.}
\title{Cartesian coordinates with an aspect ratio approximating Mercator projection.}
\usage{
coord_quickmap(xlim = NULL, ylim = NULL)
}
Expand Down Expand Up @@ -35,8 +35,8 @@ if (require("maps")) {
# Create a lat-long dataframe from the maps package
nz <- map_data("nz")
# Prepare a plot of the map
nzmap <- ggplot(nz, aes(x=long, y=lat, group=group)) +
geom_polygon(fill="white", colour="black")
nzmap <- ggplot(nz, aes(x = long, y = lat, group = group)) +
geom_polygon(fill = "white", colour = "black")

# Plot it in cartesian coordinates
nzmap
Expand Down