included suggestions

Author: veraanadi

NEWS

@@ -1,3 +1,6 @@
+* Added new function geom_curve to add curved lines to plot (similar to
+  geom_segment to add straight lines). (@veraanadi, #1088)
+
 * Create correct legend for continuous color even if there is only one color
   (@krlmlr, #943)
 

R/geom-curve.r

@@ -3,10 +3,10 @@
 #' @section Aesthetics:
 #' \Sexpr[results=rd,stage=build]{ggplot2:::rd_aesthetics("geom", "curve")}
 #'
-#' @inheritParams geom_point
-#' @param curvature see curveGrob
-#' @param angle see curveGrob
-#' @param ncp see curveGrob
+#' @inheritParams grid::curveGrob
+#' @param curvature A numeric value giving the amount of curvature. Negative values produce left-hand curves, positive values produce right-hand curves, and zero produces a straight line. (see curveGrob)
+#' @param angle A numeric value between 0 and 180, giving an amount to skew the control points of the curve. Values less than 90 skew the curve towards the start point and values greater than 90 skew the curve towards the end point. (see curveGrob)
+#' @param ncp The number of control points used to draw the curve. More control points creates a smoother curve. (see curveGrob)
 #' @param arrow specification for arrow heads, as created by arrow()
 #' @param lineend Line end style (round, butt, square)
 #' @seealso \code{\link{geom_segment}}, \code{\link{geom_path}} and \code{\link{geom_line}} for multi-
@@ -16,49 +16,51 @@
 #' # Adding curve segments
 #' library(grid) # needed for arrow function
 #' b <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
-#' b + geom_curve(aes(x = 2, y = 15, xend = 2, yend = 25, curvature = 0.2))
-#' b + geom_curve(aes(x = 2, y = 15, xend = 3, yend = 15, ncp = 2))
+#' b + geom_curve(aes(x = 2, y = 15, xend = 2, yend = 25), curvature = 0.2)
+#' b + geom_curve(aes(x = 2, y = 15, xend = 3, yend = 15), ncp = 2)
 #' b + geom_curve(aes(x = 5, y = 30, xend = 3.5, yend = 25), arrow = arrow(length = unit(0.5, "cm")))
 
 
-geom_curve <- function (mapping = NULL, data = NULL, stat = "identity",
-                        position = "identity", arrow = NULL, lineend = "butt", na.rm = FALSE, ...) {
+geom_curve <- function (mapping = NULL, data = NULL, stat = "identity", position = "identity",
+                        curvature = 1, angle = 90, ncp = 1, arrow = NULL, lineend = "butt",
+                        na.rm = FALSE, ...) {
 
   GeomCurve$new(mapping = mapping, data = data, stat = stat,
-                position = position, arrow = arrow, lineend = lineend, na.rm = na.rm, ...)
+                position = position, arrow = arrow, curvature = curvature, angle = angle,
+                ncp = ncp, lineend = lineend, na.rm = na.rm, ...)
 }
 
 GeomCurve <- proto(Geom, {
   objname <- "curve"
 
-    draw <- function(., data, scales, coordinates, arrow = NULL,
-                     lineend = "butt", na.rm = FALSE, ...) {
+    draw <- function(., data, scales, coordinates, curvature, angle, ncp,
+                     arrow, lineend, na.rm, ...) {
 
     data <- remove_missing(data, na.rm = na.rm,
-                           c("x", "y", "xend", "yend", "linetype", "size", "shape", "curvature", "angle", "ncp"),
+                           c("x", "y", "xend", "yend", "linetype", "size", "shape"),
                            name = "geom_curve")
 
     if (empty(data)) return(zeroGrob())
 
     if (is.linear(coordinates)) {
       return(with(coord_transform(coordinates, data, scales),
                   curveGrob(x, y, xend, yend, default.units="native",
-                            curvature=curvature[1], angle=angle[1], ncp=ncp[1],
+                            curvature=curvature, angle=angle, ncp=ncp,
                             square = FALSE, squareShape = 1,
                             inflect = FALSE, open = TRUE,
                             gp = gpar(col=alpha(colour, alpha), fill = alpha(colour, alpha),
                                       lwd=size * .pt, lty=linetype, lineend = lineend),
                             arrow = arrow)
       ))
     }
-    print("geom_curve is not implemented for non-linear coordinates")
+    warning("geom_curve is not implemented for non-linear coordinates")
     return(zeroGrob())
   }
 
 
   default_stat <- function(.) StatIdentity
   required_aes <- c("x", "y", "xend", "yend")
-  default_aes <- function(.) aes(colour="black", size=0.5, linetype=1, alpha = NA, curvature = 1, angle = 90, ncp = 1)
+  default_aes <- function(.) aes(colour="black", size=0.5, linetype=1, alpha = NA)
   guide_geom <- function(.) "path"
 
 })

man/geom_curve.Rd

@@ -5,39 +5,21 @@
 \title{Single curved line segments.}
 \usage{
 geom_curve(mapping = NULL, data = NULL, stat = "identity",
-  position = "identity", arrow = NULL, lineend = "butt", na.rm = FALSE,
-  ...)
+  position = "identity", curvature = 1, angle = 90, ncp = 1,
+  arrow = NULL, lineend = "butt", na.rm = FALSE, ...)
 }
 \arguments{
-\item{mapping}{The aesthetic mapping, usually constructed with
-\code{\link{aes}} or \code{\link{aes_string}}. Only needs to be set
-at the layer level if you are overriding the plot defaults.}
+\item{curvature}{A numeric value giving the amount of curvature. Negative values produce left-hand curves, positive values produce right-hand curves, and zero produces a straight line. (see curveGrob)}
 
-\item{data}{A layer specific dataset - only needed if you want to override
-the plot defaults.}
+\item{angle}{A numeric value between 0 and 180, giving an amount to skew the control points of the curve. Values less than 90 skew the curve towards the start point and values greater than 90 skew the curve towards the end point. (see curveGrob)}
 
-\item{stat}{The statistical transformation to use on the data for this
-layer.}
-
-\item{position}{The position adjustment to use for overlapping points
-on this layer}
+\item{ncp}{The number of control points used to draw the curve. More control points creates a smoother curve. (see curveGrob)}
 
 \item{arrow}{specification for arrow heads, as created by arrow()}
 
 \item{lineend}{Line end style (round, butt, square)}
 
-\item{na.rm}{If \code{FALSE} (the default), removes missing values with
-a warning.  If \code{TRUE} silently removes missing values.}
-
-\item{...}{other arguments passed on to \code{\link{layer}}. This can
-include aesthetics whose values you want to set, not map. See
-\code{\link{layer}} for more details.}
-
-\item{curvature}{see curveGrob}
-
-\item{angle}{see curveGrob}
-
-\item{ncp}{see curveGrob}
+\item{...}{Arguments to be passed to \code{curveGrob}.}
 }
 \description{
 Single curved line segments.
@@ -50,8 +32,8 @@ Single curved line segments.
 # Adding curve segments
 library(grid) # needed for arrow function
 b <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
-b + geom_curve(aes(x = 2, y = 15, xend = 2, yend = 25, curvature = 0.2))
-b + geom_curve(aes(x = 2, y = 15, xend = 3, yend = 15, ncp = 2))
+b + geom_curve(aes(x = 2, y = 15, xend = 2, yend = 25), curvature = 0.2)
+b + geom_curve(aes(x = 2, y = 15, xend = 3, yend = 15), ncp = 2)
 b + geom_curve(aes(x = 5, y = 30, xend = 3.5, yend = 25), arrow = arrow(length = unit(0.5, "cm")))
 }
 \seealso{