Draw an Xspline, a curve drawn relative to control points/observations.
Patterned after geom_line
in that it orders the points by x
first before computing the splines.
geom_xspline(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, ...) stat_xspline(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, ...)
mapping  Set of aesthetic mappings created by 

data  The data to be displayed in this layer. There are three options: If A A 
position  Position adjustment, either as a string, or the result of a call to a position adjustment function. 
na.rm  If 
show.legend  logical. Should this layer be included in the legends?

inherit.aes  If 
spline_shape  A numeric vector of values between 1 and 1, which control the shape of the spline relative to the control points. 
open  A logical value indicating whether the spline is an open or a closed shape. 
rep_ends  For open Xsplines, a logical value indicating whether the first and last control points should be replicated for drawing the curve. Ignored for closed Xsplines. 
...  Other arguments passed on to 
geom, stat  Use to override the default connection between

A sample of the output from geom_xspline()
:
An Xspline 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 Bspline 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 CatmullRom spline when the shape is 1). If the shape parameter is 0, the spline forms a sharp corner at that control point.
For open Xsplines, the start and end control points must have a shape of 0 (and nonzero values are silently converted to zero).
For open Xsplines, 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.
geom_xspline
understands the following aesthetics (required aesthetics
are in bold):
x
y
alpha
color
linetype
size
x
y
Blanc, C. and Schlick, C. (1995), "Xsplines : A Spline Model Designed for the End User", in Proceedings of SIGGRAPH 95, pp. 377386. http://deptinfo.labri.fr/~schlick/DOC/sig1.html
geom_line
: Connect observations (x order);
geom_path
: Connect observations;
geom_polygon
: Filled paths (polygons);
geom_segment
: Line segments;
xspline
;
grid.xspline
Other xspline implementations: geom_xspline2
# NOT RUN { 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) # }