Description Usage Arguments Author(s) References See Also Examples
vectorplot
displays vector fields from Raster
objects using arrows.
streamplot
displays streamlines with a procedure inspired by
the FROLIC algorithm (see references): for each point (droplet)
of a jittered regular grid, a short streamline portion
(streamlet) is calculated by integrating the underlying vector
field at that point. The main color of each streamlet indicates local
vector magnitude (slope). Streamlets are composed of points
whose sizes, positions and color degradation encode the local vector
direction (aspect).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | ## S4 method for signature 'Raster'
vectorplot(object, layers,
narrows=2e3, lwd.arrows=0.6, length=unit(5e-2, 'npc'),
maxpixels=1e5, region=TRUE,
isField=FALSE, reverse=FALSE, unit='radians', ...)
## S4 method for signature 'Raster'
streamplot(object, layers,
droplet = list(), streamlet = list(),
par.settings=streamTheme(),
isField = FALSE, reverse=FALSE,
parallel=TRUE, mc.cores=detectCores(), cl=NULL,
...)
## S4 method for signature 'RasterStack'
streamplot(object, layers,
droplet = list(), streamlet = list(),
par.settings=streamTheme(),
isField = FALSE, reverse=FALSE,
parallel=TRUE, mc.cores=detectCores(), cl=NULL,
...)
|
object |
A Raster object. If |
layers |
A numeric or character which should indicate the layers to be displayed. |
maxpixels |
A numeric, number of cells to be shown if
|
narrows |
A numeric, number of arrows. |
lwd.arrows |
Numeric, width of the lines of the arrows |
length |
Unit, extent of the arrow head. |
droplet |
A list whose elements define the droplet configuration:
|
streamlet |
A list whose elements define the streamlet configuration:
|
par.settings |
A list to define the graphical parameters. For
|
parallel |
Logical, TRUE (default) to use |
cl |
a cluster object. Read the help page of
|
mc.cores |
The number of cores to use if |
region |
Logical, if |
reverse |
Logical, TRUE if arrows or streamlets go against the direction of the gradient. |
isField |
Logical, if |
unit |
Character, angle units of the |
... |
Additional arguments for |
Oscar Perpiñán Lamigueiro
R. Wegenkittl and E. Gröller, Fast Oriented Line Integral Convolution for Vector Field Visualization via the Internet, Proceedings IEEE Visualization ’97, 1997, http://www.cg.tuwien.ac.at/research/vis-dyn-syst/frolic/frolic_crc.pdf
panel.arrows
,
levelplot
,
terrain
,
mclapply
,
parLapply
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | ## Not run:
proj <- CRS('+proj=longlat +datum=WGS84')
df <- expand.grid(x=seq(-2, 2, .01), y=seq(-2, 2, .01))
df$z <- with(df, (3*x^2 + y)*exp(-x^2-y^2))
r1 <- rasterFromXYZ(df, crs=proj)
df$z <- with(df, x*exp(-x^2-y^2))
r2 <- rasterFromXYZ(df, crs=proj)
df$z <- with(df, y*exp(-x^2-y^2))
r3 <- rasterFromXYZ(df, crs=proj)
s <- stack(r1, r2, r3)
names(s) <- c('R1', 'R2', 'R3')
vectorplot(r1)
vectorplot(r2, par.settings=RdBuTheme())
vectorplot(r3, par.settings=PuOrTheme())
## If no cluster is provided, streamplot uses parallel::mclapply except
## with Windows. Therefore, next code could spend a long time under
## Windows.
streamplot(r1)
## With a cluster
hosts <- rep('localhost', 4)
cl <- makeCluster(hosts)
streamplot(r2, cl=cl,
par.settings=streamTheme(symbol=brewer.pal(n=5,
name='Reds')))
stopCluster(cl)
## Without parallel
streamplot(r3, parallel=FALSE,
par.settings=streamTheme(symbol=brewer.pal(n=5,
name='Greens')))
## Configuration of droplets and streamlets
streamplot(s, layout=c(1, 3), droplet=list(pc=.2), streamlet=list(L=20),
par.settings=streamTheme(cex=.6))
## End(Not run)
|
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