Sean O'Riordain wrote:
Hi Laura,
you should find some useful information in the latest R news Volume 3/2, October 2003
http://cran.r-project.org/doc/Rnews/
refer page 8 where Paul's figure 2 shows some novel symbols showing "China Sea Wind Speed, Direction and Temperature"... plotted by lat.&long.
Sorry Laura, I saw the original mail, got interested in the animation part, then got distracted :) As Sean has pointed out, the wind vectors could be done like the example in the R News article, but that may not be appropriate if there are very many to be drawn (could get slow). Here's a modification of that example which just draws wind vectors as simple arrows...
library(gridBase) chinasea <- read.table("chinasea.txt", header=TRUE) plot(chinasea$lat, chinasea$long, type="n", xlab="latitude", ylab="longitude", main="China Sea Wind Speed/Direction and Temperature") speed <- 0.8*chinasea$speed/14 + 0.2 temp <- chinasea$temp/40 vps <- baseViewports() par(new=TRUE) push.viewport(vps$inner, vps$figure, vps$plot)
# Just use a grid.arrows instead of a whole viewport per symbol
length <- 1 # "cm"
x1 <- unit(chinasea$lat, "native") -
unit(0.5*length*cos(pi*chinasea$dir/180), "cm")
y1 <- unit(chinasea$long, "native") -
unit(0.5*length*sin(pi*chinasea$dir/180), "cm")
x2 <- unit(chinasea$lat, "native") +
unit(0.5*length*cos(pi*chinasea$dir/180), "cm")
y2 <- unit(chinasea$long, "native") +
unit(0.5*length*sin(pi*chinasea$dir/180), "cm")
grid.arrows(grob=grid.segments(x1, y1, x2, y2),
length=unit(3, "mm"))pop.viewport(3)
... This modification still requires gridBase; the same effect could be achieved with the base arrows() function, i.e., without gridBase, with a little more effort required to calculate the "x" and "y" values for the arrows.
You might also want to take a look at http://sal.agecon.uiuc.edu/csiss/Rgeo/index.html
which gives an overview of the packages related to spatial statistics that are available for R. Somebody may have already done all the work for you :)
Paul
Laura Quinn wrote:
I sent a mail last week asking for some advise in relation to displaying wind vectors on a contour map of a region. Whilst I have had some useful feedback relating to the second part of this question (namely how to animate a time series of still frames), I haven't recieved any advise on how I might create the still images of the spatially distributed wind vector data at any given time point.
Firstly, is there a way in which I can input orographical information (x,y,z co ords) into R to create a map, secondly, is there a way in which i can superimpose a visual wind vector (i.e. arrow of certain length and certain orientation) onto such a map?
thanks in advance, Laura
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-- Dr Paul Murrell Department of Statistics The University of Auckland Private Bag 92019 Auckland New Zealand 64 9 3737599 x85392 [EMAIL PROTECTED] http://www.stat.auckland.ac.nz/~paul/
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