[R-sig-Geo] Plotting direction vectors from an aspect map

[Oscar Perpiñan Lamigueiro]

Hi,

I have uploaded a first draft of a vectorplot function in rasterVis. It
is available here:
https://r-forge.r-project.org/scm/viewvc.php/drafts/vectorplot.R?view=markup&root=rastervis.
It uses the raster::slopeAspect function to calculate the slope/aspect
from a raster object. 

For example:

library(raster)
library(rasterVis)

df <- expand.grid(x=seq(-2, 2, .1), y=seq(-2, 2, .1))
df$z <- with(df, (3*x^2 + y)*exp(-x^2-y^2))
r1 <- rasterFromXYZ(df)
df$z <- with(df, x*exp(-x^2-y^2))
r2 <- rasterFromXYZ(df)
df$z <- with(df, y*exp(-x^2-y^2))
r3 <- rasterFromXYZ(df)

projection(r1) <- projection(r2) <- projection(r3) <-
CRS("+proj=longlat +datum=WGS84")

vectorplot(r1, par.settings=RdBuTheme)
vectorplot(r2, par.settings=RdBuTheme)
vectorplot(r3, par.settings=RdBuTheme)

I will include it in the rasterVis package after some tests.

Best,

Oscar.

-------------
Oscar Perpiñán Lamigueiro
Dpto. de Ingeniería Eléctrica
EUITI-UPM

http://procomun.wordpress.com
> >> >  -----Original Message-----
> >> >  From:r-sig-geo-bounces at r-project.org
> >> > [mailto:r-sig-geo-bounces at r- project.org] On Behalf Of Jonathan
> >> > Greenberg Sent: Thursday, September 15, 2011 7:18 PM
> >> >  To: r-sig-geo
> >> >  Subject: [R-sig-Geo] Plotting direction vectors from an aspect
> >> > map 
> >> >  R-sig-geo'ers:
> >> >  
> >> >  Given an aspect raster (GDAL-readable), is there a way to plot
> >> > the aspect image using arrows representing each cell's
> >> > direction?  I'm assuming I have to convert the raster to a set
> >> > of points -- are there arrow symbols and, if so, can you rotate
> >> > them based on some parameter? 
> >> >  Thanks!
> >> >  
> >> >  --j
> >> >  
> >> >  --
> >> >  Jonathan A. Greenberg, PhD
> >> >  Assistant Project Scientist
> >> >  Center for Spatial Technologies and Remote Sensing (CSTARS)
> >> >  Department of Land, Air and Water Resources
> >> >  University of California, Davis
> >> >  One Shields Avenue
> >> >  Davis, CA 95616
> >> >  Phone: 415-763-5476
> >> >  AIM: jgrn307, MSN:jgrn307 at hotmail.com, Gchat: jgrn307
> >> >  
> >> >  _______________________________________________
> >> >  R-sig-Geo mailing list
> >> >  R-sig-Geo at r-project.org
> >> >  https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>