How to map wind direction and speed (velocity plot) with R

Question

Basically I have lists with 2 matrices (u and v) containing the windspeed in longitudal and latitudal direction (and vectors x and y containing the coordinates). I would like to make a map with arrows pointing in the resulting direction, of which the size is proportional to the wind speed. This question was asked before: http://www.mail-archive.com/r-help@r-project.org/msg18875.html. Uforunately, the link given in the answer is broken. I tried using the quiver function, but I don't get it working.

Here is how my data looks like:

x=seq(10,15,by=0.25)
y=seq(40,50,by=0.25)
u=matrix(runif(length(x)*length(y),-2,3),nrow=length(y),ncol=length(y))
v=matrix(runif(length(x)*length(y),-2,3),nrow=length(y),ncol=length(y))
wind=list(u,v)

For the quiver function:

library(pracma)
quiver(x=x, y=y, u=wind[[1]], v=wind[[2]])

Which gives twice:

Error: invalid graphics state

I assume that u and v are wrong and need to be coordinates as well, but I honestly don't understand the explanation given in the package discription (u, v : x,y-coordinates of start points).

I saw that more info is available for quiver in matlab or python, but I never worked with that, so any advice about doing this in R would be greatly appreciated.

Answer 1

x=seq(10,15,by=0.25)
y=seq(40,50,by=0.25)
u=matrix(runif(length(x)*length(y),-2,3),nrow=length(x),ncol=length(y))
v=matrix(runif(length(x)*length(y),-2,3),nrow=length(x),ncol=length(y))
#note that I corrected these

#melt for plotting
library(reshape2)
u <- melt(u,value.name = "u")
v <- melt(v,value.name = "v")
wind <- merge(u, v)
wind$x <- x[wind[,1]]
wind$y <- y[wind[,2]]


#plot
library(ggplot2)
library(grid)
scaler <- 1

p <- ggplot(wind, aes(x=x, y=y, xend=x+u*scaler, yend=y+v*scaler)) + geom_segment(arrow=arrow())
print(p)