https://github.com/cran/fields
Tip revision: 04279c16ce718b82025aae97f6fcd30ba3a8b1c5 authored by Doug Nychka on 05 September 2011, 20:18:33 UTC
version 6.6
version 6.6
Tip revision: 04279c1
arrow.plot.R
# fields, Tools for spatial data
# Copyright 2004-2011, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
"arrow.plot" <- function(a1, a2, u = NA, v = NA, arrow.ex = 0.05,
xpd = TRUE, true.angle = FALSE, arrowfun = arrows, ...) {
if (is.matrix(a1)) {
x <- a1[, 1]
y <- a1[, 2]
}
else {
x <- a1
y <- a2
}
if (is.matrix(a2)) {
u <- a2[, 1]
v <- a2[, 2]
}
ucord <- par()$usr
arrow.ex <- arrow.ex * min(ucord[2] - ucord[1], ucord[4] -
ucord[3])
if (true.angle) {
pin <- par()$pin
r1 <- (ucord[2] - ucord[1])/(pin[1])
r2 <- (ucord[4] - ucord[3])/(pin[2])
}
else {
r1 <- r2 <- 1
}
u <- u * r1
v <- v * r2
maxr <- max(sqrt(u^2 + v^2))
u <- (arrow.ex * u)/maxr
v <- (arrow.ex * v)/maxr
invisible()
old.xpd <- par()$xpd
par(xpd = xpd)
arrowfun(x, y, x + u, y + v, ...)
par(xpd = old.xpd)
}