| get_iso_polys {CCAMLRGIS} | R Documentation |
Generate contour polygons from raster
Description
From an input raster and chosen cuts (classes), turns areas between contours into polygons.
An input polygon may optionally be given to constrain boundaries.
The accuracy is dependent on the resolution of the raster
(e.g., see load_Bathy to get high resolution bathymetry).
Usage
get_iso_polys(
Rast,
Poly = NULL,
Cuts,
Cols = c("green", "yellow", "red"),
Grp = FALSE
)
Arguments
Rast |
raster with the appropriate projection, such as
|
Poly |
optional, single polygon inside which contour polygons will be generated.
May be created using |
Cuts |
numeric, vector of desired contours. For example,
|
Cols |
character, vector of desired colors (see |
Grp |
logical (TRUE/FALSE), if set to TRUE (slower), contour polygons that touch each other are identified and grouped (a Grp column is added to the object). This can be used, for example, to identify seamounts that are constituted of several isobaths. |
Value
Spatial object in your environment. Data within the resulting object contains
a polygon in each row. Columns are as follows: ID is a unique polygon identifier;
Iso is a contour polygon identifier; Min and Max are the range of contour values;
c is the color of each contour polygon; if Grp was set to TRUE, additional columns are:
Grp is a group identifier (e.g., a seamount constituted of several isobaths);
AreaKm2 is the polygon area in square kilometers; Labx and Laby can be used
to label groups (see GitHub example).
See Also
load_Bathy, create_Polys, get_depths.
Examples
# For more examples, see:
# https://github.com/ccamlr/CCAMLRGIS#46-get_iso_polys
Poly=create_Polys(Input=data.frame(ID=1,Lat=c(-55,-55,-61,-61),Lon=c(-30,-25,-25,-30)))
IsoPols=get_iso_polys(Rast=SmallBathy(),Poly=Poly,Cuts=seq(-8000,0,length.out=10),Cols=rainbow(9))
plot(st_geometry(Poly))
plot(st_geometry(IsoPols),col=IsoPols$c,add=TRUE)