Create a conical gradient of interpolated values around a point
Source:R/radar_cone.R
radar_cone.Rd
Using a given coordinate, this function will generate a circle of a given radius around the point and fill the circle with a gradient of values in a conical pattern. By default, the interpolated values range from zero to one, with values of one point in the direction of the specified heading.
Usage
radar_cone(
pt,
radius,
heading,
theta = 0,
res = 500,
mask = TRUE,
invert = FALSE,
maxvalue = 1
)
Arguments
- pt
A single (X,Y) coordinate of class
sfc_POINT
(created by thesf
package), where the CRS is a projected coordinate system.- radius
Numeric. Distance in meters from the point
pt
to draw the circle radius.- heading
Numeric. Heading, in compass degrees, which to interpolate values from.
- theta
Numeric (0 to 360). Angle, in degrees, indicating the amount of the circle that should be taken up by the
maxvalue
. For example, if you want to create a wedge where 1/3 of the circle == 1, settheta = 120
. Default0
.- res
Numeric. Resolution, in meters, of the output raster. Default
500
.- mask
Boolean (TRUE/FALSE). Should the output be masked to a circle shape (rather than square)? Default
TRUE
.- invert
Boolean (TRUE/FALSE). Should the values of the output cone be inverted, such that the values in the direction of the heading are 0 rather than 1? Default
FALSE
.- maxvalue
Numeric. Maximum value of the interpolated values of the cone. The interpolated values run from 0 to
maxvalue
. Default1
.
Details
When using this function with spatial features, ensure your data are projected in an equal-area coordinate system. This function assumes meters as the default unit.
This function was originally developed with the intention of generating 'cones of probability' for estimating the dispersal of birds flying across a landscape. Radar stations based across British Columbia, Canada, collected data on the mean headings of birds flying across a radar station. These headings indicate the more likely direction birds will be flying to, while headings in the opposite direction indicate areas the birds are flying away from. Thus, the gradient of values from 0 (flying away) to 1 (flying towards) was developed around each given radar station using this function.