[R] Hydrology plots in R

[Jim Lemon]

On 07/23/2010 12:56 AM, Sam Albers wrote:
> Hello,
>
> I am trying to create a plot often seen in hydrodynamic work than includes a
> contour plot representing the water speed with arrows pointing in the
> direction of flow. Does anyone have any idea how I might add arrows based on
> wf$angle (in the example below) to the plot below?
>
> Thanks in advance!
>
> Sam
>
> library(lattice)
>
> speed<- runif(100, 0, 20)
> wf<- data.frame(speed)
> wf$width<- (1:10)
> wf$length<- rep(1:10, each=10)
> wf$angle<-runif(100, 0, 360)
>
> #How do I add arrows based on wf$angle within each coloured box to represent
> the direction of flow?
> #i don't have to use lattice. Just using it as an example.
> with(wf, contourplot(speed ~ width*length,
>                       region=TRUE,
>                       contour=FALSE
>                       ))
>

Hi Sam,
Try this solution from the plotrix package:

par(mar=c(5,4,4,4))
color2D.matplot(matrix(wf$speed,ncol=10),extremes=c("#88eeee","#ee88ee"))
color.legend(10.6,0,11.1,10,seq(-5,25,by=5),color.scale(seq(-5,25,by=5),
  extremes=c("#88eeee","#ee88ee")),gradient="y")
vectorField(matrix(wf$angle,ncol=10),matrix(0.5,nrow=10,ncol=10),
  xpos=matrix(0.5:9.5,nrow=10,ncol=10,byrow=TRUE),
  ypos=matrix(9.5:0.5,nrow=10,ncol=10),scale=0.5,vecspec="deg")

I probably don't have the values lined up correctly.

Jim