Dear list,
I would like to plot arrows with different colors according to arrow length,
and also (if
possible) with head size proportional to arrow length. The idea is to make a
quiver-like plot of
matlab with wind speed data.
So far, I´ve been able to use different colors, but I need to find a more
efficient way to recode
arrow length intervals into colors. On the contrary, I can't define different
head sizes, because
the "length" argument in the "arrows()" function seems to control the head size
of all the
arrows at once.
Any help will be greatly appreciated.
## Generate random data
set.seed(1)
xcoor <- matrix(runif(20), ncol=5)
ycoor <- matrix(runif(20), ncol=5)
u <- matrix(rnorm(20)/10, ncol=5)
v <- matrix(rnorm(20)/10, ncol=5)
## calculate arrows length and look histogram
arrowlen <- sqrt(u^2 + v^2)
hist(arrowlen)
## recode arrow lengths (by interval) into colors
## sorry, I don't know how to do it without the car package
library(car)
arrowL <- recode(as.vector(arrowlen),
"0='grey90';
0:0.05='grey50';
0.05:0.1='grey';
0.1:0.15='cyan';
0.15:0.2='blue';
0.2:0.25='red'")
length=0.1
par.uin <- function()
# determine scale of inches/userunits in x and y
# from http://tolstoy.newcastle.edu.au/R/help/01c/2714.html
# Brian Ripley Tue 20 Nov 2001 - 20:13:52 EST
{
u <- par("usr")
p <- par("pin")
c(p[1]/(u[2] - u[1]), p[2]/(u[4] - u[3]))
}
## plot arrows
plot(as.vector(xcoor), as.vector(ycoor), type="p", pch=".", xlim=c(-0.2, 1.3),
ylim=c(-0.2, 1.3))
arrows( xcoor, ycoor, xcoor + u, ycoor + v,
length = length*as.vector(arrowlen)*min(par.uin()), col=arrowL)
> sessionInfo()
R version 2.8.1 (2008-12-22)
i386-pc-mingw32
locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods
[7] base
other attached packages:
[1] car_1.2-9 hdf5_1.6.7
--
Héctor Villalobos <hvill...@ipn.mx>
CICIMAR - IPN
La Paz, Baja California Sur, MÉXICO
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