Extra Coordinate Systems, 'Geoms', Statistical Transformations, Scales and Fonts for 'ggplot2'
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 #' Connect control points/observations with an X-spline #' #' Draw an X-spline, a curve drawn relative to control points/observations. #' Patterned after \code{geom_line} in that it orders the points by \code{x} #' first before computing the splines. #' #' \if{html}{ #' A sample of the output from \code{geom_xspline()}: #' #' \figure{geomxspline01.png}{options: width="100\%" alt="Figure: geomxspline01.png"} #' } #' #' \if{latex}{ #' A sample of the output from \code{geom_xspline()}: #' #' \figure{geomxspline01.png}{options: width=10cm} #' } #' #' @section Aesthetics: #' \code{geom_xspline} understands the following aesthetics (required aesthetics #' are in bold): #' \itemize{ #' \item \strong{\code{x}} #' \item \strong{\code{y}} #' \item \code{alpha} #' \item \code{color} #' \item \code{linetype} #' \item \code{size} #' } #' #' @seealso #' \code{\link[ggplot2]{geom_line}}: Connect observations (x order); #' \code{\link[ggplot2]{geom_path}}: Connect observations; #' \code{\link[ggplot2]{geom_polygon}}: Filled paths (polygons); #' \code{\link[ggplot2]{geom_segment}}: Line segments; #' \code{\link[graphics]{xspline}}; #' \code{\link[grid]{grid.xspline}} #' #' @details #' An X-spline is a line drawn relative to control points. For each control #' point, the line may pass through (interpolate) the control point or it may #' only approach (approximate) the control point; the behaviour is determined #' by a shape parameter for each control point. #' #' If the shape parameter is greater than zero, the spline approximates the #' control points (and is very similar to a cubic B-spline when the shape is #' 1). If the shape parameter is less than zero, the spline interpolates the #' control points (and is very similar to a Catmull-Rom spline when the shape #' is -1). If the shape parameter is 0, the spline forms a sharp corner at that #' control point. #' #' For open X-splines, the start and end control points must have a shape of #' 0 (and non-zero values are silently converted to zero). #' #' For open X-splines, by default the start and end control points are #' replicated before the curve is drawn. A curve is drawn between (interpolating #' or approximating) the second and third of each set of four control points, #' so this default behaviour ensures that the resulting curve starts at the #' first control point you have specified and ends at the last control point. #' The default behaviour can be turned off via the repEnds argument. #' #' @inheritParams ggplot2::geom_line #' @param geom,stat Use to override the default connection between #' \code{geom_xspline} and \code{stat_xspline}. #' @param spline_shape A numeric vector of values between -1 and 1, which #' control the shape of the spline relative to the control points. #' @param open A logical value indicating whether the spline is an open or a #' closed shape. #' @param rep_ends For open X-splines, a logical value indicating whether the #' first and last control points should be replicated for drawing the #' curve. Ignored for closed X-splines. #' @references Blanc, C. and Schlick, C. (1995), "X-splines : A Spline Model #' Designed for the End User", in \emph{Proceedings of SIGGRAPH 95}, #' pp. 377-386. \url{http://dept-info.labri.fr/~schlick/DOC/sig1.html} #' @export #' @family xspline implementations #' @examples #' set.seed(1492) #' dat <- data.frame(x=c(1:10, 1:10, 1:10), #' y=c(sample(15:30, 10), 2*sample(15:30, 10), #' 3*sample(15:30, 10)), #' group=factor(c(rep(1, 10), rep(2, 10), rep(3, 10))) #' ) #' #' ggplot(dat, aes(x, y, group=group, color=group)) + #' geom_point() + #' geom_line() #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point() + #' geom_line() + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(spline_shape=-0.4, size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(spline_shape=0.4, size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(spline_shape=1, size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(spline_shape=0, size=0.5) #' #' ggplot(dat, aes(x, y, group=group, color=factor(group))) + #' geom_point(color="black") + #' geom_smooth(se=FALSE, linetype="dashed", size=0.5) + #' geom_xspline(spline_shape=-1, size=0.5) geom_xspline <- function(mapping = NULL, data = NULL, stat = "xspline",  position = "identity", na.rm = TRUE, show.legend = NA,  inherit.aes = TRUE,  spline_shape=-0.25, open=TRUE, rep_ends=TRUE, ...) {  layer(  geom = GeomXspline,  mapping = mapping,  data = data,  stat = stat,  position = position,  show.legend = show.legend,  inherit.aes = inherit.aes,  params = list(  spline_shape = spline_shape,  open = open,  na.rm = na.rm,  rep_ends = rep_ends,  ...  )  ) }   #' Geom Proto #' @rdname ggalt-ggproto #' @format NULL #' @usage NULL #' @keywords internal #' @export GeomXspline <- ggproto("GeomXspline", GeomLine,  required_aes = c("x", "y"),  default_aes = aes(colour = "black", size = 0.5, linetype = 1, alpha = NA) )   #' @export #' @rdname geom_xspline #' @section Computed variables: #' \itemize{ #' \item{x} #' \item{y} #' } stat_xspline <- function(mapping = NULL, data = NULL, geom = "line",  position = "identity", na.rm = TRUE, show.legend = NA, inherit.aes = TRUE,  spline_shape=-0.25, open=TRUE, rep_ends=TRUE, ...) {  layer(  stat = StatXspline,  data = data,  mapping = mapping,  geom = geom,  position = position,  show.legend = show.legend,  inherit.aes = inherit.aes,  params = list(spline_shape=spline_shape,  open=open,  na.rm = na.rm,  rep_ends=rep_ends,  ...  )  ) }   #' @rdname ggalt-ggproto #' @format NULL #' @usage NULL #' @export StatXspline <- ggproto("StatXspline", Stat,    required_aes = c("x", "y"),    compute_group = function(self, data, scales, params,  spline_shape=-0.25, open=TRUE, rep_ends=TRUE) {    tf <- tempfile(fileext=".png")  png(tf)  plot.new()  tmp <- xspline(data$x, data$y, spline_shape, open, rep_ends, draw=FALSE, NA, NA)  invisible(dev.off())  unlink(tf)    data.frame(x=tmp$x, y=tmp$y)  }   )