| extract_rr | R Documentation | 
Compute relative radiance at selected sky points by dividing their digital numbers (DN) by an estimated zenith DN.
extract_rr(r, z, a, sky_points, no_of_points = 3, use_window = TRUE)
| r | terra::SpatRaster. Raster supplying the DN values; must
share rows and columns with the image used to obtain  | 
| z | terra::SpatRaster generated with  | 
| a | terra::SpatRaster generated with  | 
| sky_points | 
 | 
| no_of_points | numeric vector of length one or  | 
| use_window | logical of length one. If  | 
List with named elements:
zenith_dnnumeric. Estimated DN at the zenith.
sky_pointsdata.frame with columns row, col, a, z, dn,
and rr (pixel location, angular coordinates, extracted DN, and relative
radiance). If no_of_points is NULL, zenith_dn = 1 and dn = rr.
## Not run: 
caim <- read_caim()
z <- zenith_image(ncol(caim), lens())
a <- azimuth_image(z)
# See fit_cie_model() for details on the CSV file
path <- system.file("external/sky_points.csv",
                    package = "rcaiman")
sky_points <- read.csv(path)
sky_points <- sky_points[c("Y", "X")]
colnames(sky_points) <- c("row", "col")
head(sky_points)
plot(caim$Blue)
points(sky_points$col, nrow(caim) - sky_points$row, col = 2, pch = 10)
rr <- extract_rr(caim$Blue, z, a, sky_points, 1)
points(rr$sky_points$col, nrow(caim) - rr$sky_points$row, col = 3, pch = 0)
## End(Not run)
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