Dear all,
I feel like I've been reinventing the wheel with this code (implementing
type = 'b' for Grid graphics),
http://econum.umh.ac.be/rwiki/doku.php?id=tips:graphics-grid:linesandpointsgrob
Has anyone here attempted this with success before? I found suggestions
of overlapping large white points to mask the lines but it's not ideal.
I welcome any comments on the code. (e.g., should it perhaps use
polylines rather than segments?, is there an obvious optimization to
make?, ...)
Regards,
baptiste
# code reproduced below,
barbedGrob <- function( x = 1:10/12,
y = sin(1:10)/3+0.5,
size=1, shape=21, space=1,
colour="red", fill="blue",
linetype=1, linewidth=1){
n <- length(x)
dx <- diff(x)
dy <- diff(y)
# duplicate the points to make split segments
new.x <- rep(x, each=2)[-c(1, 2*length(x))]
new.y <- rep(y, each=2)[-c(1, 2*length(y))]
new.size <- rep(size, each=2, length=2*n)[-c(1, 2*n)]
length <- sqrt(dx^2 + dy^2) # length of initial segments
exclusion <- 0.5*space*convertX(unit(new.size, "char"), "npc", TRUE)
scaling <- exclusion / rep(length, each=2) # exclusion factor around
each point
start <- seq(1, by=2, length(new.x)) # starting points
end <- seq(2, by=2, length(new.x)) # end points
x.start <- scaling[start] * dx[(start+1)/2] + new.x[start] # shift the
points
y.start <- scaling[start] * dy[(start+1)/2] + new.y[start] # keeping the
direction of the initial segments
x.end <- new.x[end] - scaling[end] * dx[end/2]
y.end <- new.y[end] - scaling[end] * dy[end/2]
grob.lines <- segmentsGrob(
x0 = x.start, y0 = y.start,
x1 = x.end, y1=y.end,
default.units="native",
gp = gpar(
col = colour,
lex = linewidth, lty = linetype, lineend = "butt"
)
)
grob.points <- pointsGrob(x, y, pch=shape, size=unit(size, "char"),
gp = gpar(
col = colour,
fill = fill,
lex = linewidth, linejoin = "mitre"
)
)
gTree(children = gList(grob.lines,grob.points))
}
# example of use
g <-
barbedGrob(size=sample(1:3, 10, repl=T),
fill=alpha("white", 0.3),
col=alpha("cadetblue4", 0.8),
linewidth=5, space=1.2)
pushViewport(vp=viewport(width=1, height=1))
grid.rect(gp=gpar(fill="thistle2"))
grid.grill(gp=gpar(col="lavenderblush1", lwd=3, lty=3))
grid.draw(g)
--
_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
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