oce (version 0.9-18)

mapDirectionField: Plot a direction field on a existing map

Description

Plot a direction field on a existing map

Usage

mapDirectionField(longitude, latitude, u, v,
                  scale=1, length=0.05, code=2, col=par("fg"), ...)

Arguments

longitude, latitude

starting points for arrows

u, v

components of a vector to be shown as a direction field

scale

latitude degrees per unit of u or v.

length

length of arrow heads, passed to arrows

code

code of arrows, passed to arrows

col

colour of arrows. This may be a single colour, or a matrix of colours of the same dimension as u.

...

optional arguments passed to arrows, e.g. angle and lwd can be useful in differentiating different fields.

Details

Adds arrows for a direction field on an existing map. There are different possibilities for how longitude, latitude and u and v match up. In one common case, all four of these are matrices, e.g. output from a numerical model. In another, longitude and latitude are the coordinates along the matrices, and are thus stored in vectors with lengths that match appropriately.

See Also

See mapPlot for general information on plotting maps, including other functions.

Examples

library(oce)
data(coastlineWorld)
par(mar=rep(2,4))
mapPlot(coastlineWorld, longitudelim=c(-120,-55), latitudelim=c(35,50),
        proj="lambert", parameters=c(lat0=40,lat1=60),
        orientation=c(90,-90,0))
lon <- seq(-120, -60, 15)
lat <- 45 + seq(-15, 15, 5)
lonm <- matrix(expand.grid(lon,lat)[,1], nrow=length(lon))
latm <- matrix(expand.grid(lon,lat)[,2], nrow=length(lon))
## vectors pointed 45 degrees clockwise from north
u <- matrix(1/sqrt(2), nrow=length(lon), ncol=length(lat))
v <- matrix(1/sqrt(2), nrow=length(lon), ncol=length(lat))
mapDirectionField(lon, lat, u, v, scale=3)
mapDirectionField(lonm, latm, 0, 1, scale=3, col='red')
# Color code by longitude, using thick lines
col <- colormap(lonm)$zcol
mapDirectionField(lonm, latm, 1, 0, scale=3, col=col, lwd=2)