add_grid

R/plot_legend.R

@@ -506,4 +506,33 @@ add_box <- function(...) {
 }
 
 
+add_grid <- function(nx = NULL, ny = nx, col = "lightgray", lty = "dotted", lwd = par("lwd"), equilogs = TRUE) {
+
+
+	p <- terra:::get.clip()
+
+	## adapted from graphics::grid 
+	g.grid.at <- function (side, n, log, equilogs, axp, usr2) {
+		if (is.null(n)) {
+			stopifnot(is.numeric(ax <- axp), length(ax) == 3L)
+			if (log && equilogs && ax[3L] > 0) 
+				ax[3L] <- 1
+			axTicks(side, axp = ax, usr = usr2, log = log)
+		}
+		else if (!is.na(n) && (n <- as.integer(n)) >= 1L) {
+			at <- seq.int(usr2[1L], usr2[2L], length.out = n + 1L)
+			(if (log) 
+				10^at
+			else at)[-c(1L, n + 1L)]
+		}
+	}
+
+    atx <- if (is.null(nx) || (!is.na(nx) && nx >= 1)) 
+        g.grid.at(1L, nx, log = par("xlog"), equilogs, axp = par("xaxp"), usr2 = p[1:2])
+    aty <- if (is.null(ny) || (!is.na(ny) && ny >= 1)) 
+        g.grid.at(2L, ny, log = par("ylog"), equilogs, axp = par("yaxp"), usr2 = p[3:4])
+    abline(v = atx, h = aty, col = col, lty = lty, lwd = lwd)
+    invisible(list(atx = atx, aty = aty))
+}
+
 

man/box.Rd

@@ -5,7 +5,7 @@
 \title{draw a box}
 
 \description{ 
-Similar to \code{\link{box}} allowing adding a box around a map. This function will place the legend in the locations within the mapped area as delineated by the axes.
+Similar to \code{\link[graphics]{box}} allowing adding a box around a map. This function will place the legend in the locations within the mapped area as delineated by the axes.
 }
 
 \usage{
@@ -17,6 +17,8 @@ add_box(...)
 }
 
 
+\seealso{\code{\link{add_legend}}, \code{\link{add_grid}}}
+
 \examples{
 v <- vect(system.file("ex/lux.shp", package="terra"))
 plot(v)

man/grid.Rd

@@ -0,0 +1,36 @@
+\name{add_grid}
+
+\alias{add_grid}
+
+\title{add a grid to an existing terra plot}
+
+\description{ 
+Wrapper around \code{\link[graphics]{grid}} that allows adding a grid to a map. This function will place the legend in the locations within the mapped area as delineated by the axes.
+
+Also see \code{\link{graticule}}
+}
+
+\usage{
+add_grid(nx = NULL, ny = nx, col = "lightgray", lty = "dotted",
+     lwd = par("lwd"), equilogs = TRUE)
+}
+
+\arguments{
+  \item{nx, ny}{number of cells of the grid in x and y direction. When NULL, as per default, the grid aligns with the tick marks on the corresponding default axis (i.e., tickmarks as computed by axTicks). When NA, no grid lines are drawn in the corresponding direction}
+  \item{col}{character or (integer) numeric; color of the grid lines}
+  \item{lty}{character or (integer) numeric; line type of the grid lines}
+  \item{lwd}{non-negative numeric giving line width of the grid lines}
+  \item{equilogs}{logical, only used when log coordinates and alignment with the axis tick marks are active. Setting equilogs = FALSE in that case gives non equidistant tick aligned grid lines}
+}
+
+\seealso{\code{\link{add_box}}, \code{\link{add_grid}}, \code{\link{graticule}}
+
+\examples{
+v <- vect(system.file("ex/lux.shp", package="terra"))
+plot(v)
+add_grid()
+}
+
+\keyword{methods}
+\keyword{spatial}
+

man/legend.Rd

@@ -12,13 +12,16 @@ Wrapper around \code{\link{legend}} that allows adding a custom legend to a map
 add_legend(x, y, ...)
 }
 
+
 \arguments{
   \item{x}{The keyword to be used to position the legend (or the x coordinate)}
   \item{y}{The y coordinate to be used to position the legend (is x is also a coordinate)}
   \item{...}{arguments passed to \code{\link{legend}}}
 }
 
 
+\seealso{\code{\link{add_box}}, \code{\link{add_grid}}}
+
 \examples{
 v <- vect(system.file("ex/lux.shp", package="terra"))
 plot(v)