[R] How to plot wind direction and strength field

[Greg Snow]

Does the following do what you want (or at least move in that
direction)?

u <- array(NA,c(5,8))
t <- seq(from=0.5, to=0.11,length=15)
t2 <- seq(from=(-0.7),to=(-0.1),length=25)
u[1:15] <- t
u[16:40] <- t2
v <- array(NA,c(5,8))
y <- seq(from=(-0.9), to=(-0.01),length=40) 
v[1:40] <- y

library(TeachingDemos)

library(maps)
map('state',col='grey')

lats <- seq( 27.5, 48.7, length=5 )
longs <- seq( -123, -73, length=8 )

x <- longs[ col(u) ]
y <- lats[ row(u) ]

speed <- sqrt( u*u+v*v )
dir <- atan2(v,u)

my.symbols(x,y,ms.arrows, angle=dir, r=speed, add=TRUE, length=.05)


Hope this helps,


-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
(801) 408-8111
 
 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Jenny Barnes
> Sent: Tuesday, April 29, 2008 6:26 AM
> To: Jim Lemon
> Cc: r-help at r-project.org
> Subject: Re: [R] How to plot wind direction and strength field
> 
> Thanks Jim - here is some data:
> 
> u <- array(NA,c(5,8))
> t <- seq(from=0.5, to=0.11,length=15)
> t2 <- seq(from=(-0.7),to=(-0.1),length=25)
> u[1:15] <- t
> u[16:40] <- t2
> v <- array(NA,c(5,8))
> y <- seq(from=(-0.9), to=(-0.01),length=40) v[1:40] <- y
> 
> I've made up the data but it's similar magnitude and the 
> longitude direction is u and latitude direction is v as in 
> the real data.
> 
> I really appreciate your help!
> 
> Jenny
> 
> On Tue, 29 Apr 2008, Jim Lemon wrote:
> 
> > Jenny Barnes wrote:
> >> Hi Jim,
> >> 
> >> I would like to plot something like figure 2 on this webpage:
> >> http://www.cnrfc.noaa.gov/storm_summaries/jan1997storms.php
> >> 
> >> My data is very large - covering the whole globe at 2.5deg 
> resolution 
> >> so
> >> longitude=144 girds, latitude=73 grids and time=32 years - hard to 
> >> give you that data......Would it help to give you a couple of grid 
> >> squares worth of data for one year?
> >> 
> > Okay, Figures 2 and 3 look like 5 degree squares, and given 
> a larger 
> > plot,
> > 2.5 degree should be okay. Do you want curved arrows? That 
> would take 
> > some programming as the standard arrows are straight. Also, 
> the arrows 
> > in the figures all seem to be the same length. I can make 
> the lengths 
> > proportional to wind speed. Yes, some data would be helpful, as 
> > getting the right plot usually involves trying out real 
> data. Doesn't 
> > matter if it's faked as long as it has the same format and 
> similar numbers to the real thing.
> >
> > Jim
> >
> >
> >
> 
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