make_circ_mask: Make a circular mask

In slga: Data Access Tools for the Soil and Landscape Grid of Australia

Description

Generates a circular masking matrix

Usage

make_circ_mask(buff = NULL)

Arguments

buff	The number of cells away from the central cell to mask. The return matrix will have dimensions of '(2 * buff) + 1'.

Value

Masking matrix for use in point queries with values of 0 in the 'keep zone' and NA otherwise.

Note

adapted from https://scrogster.wordpress.com/2012/10/05/applying-a-circular-moving-window-filter-to-raster-data-in-r/ . Used in SLGA when getting summary statistics around points, but can potentially be applied to any raster/point data combination. See recipe below.

Examples

 library(raster)
 library(sf)
 library(slga)
 # concept demo
 plot(sf::st_buffer(sf::st_point(c(0,0)), 5), axes = TRUE, reset = FALSE)
 plot(raster::raster(slga:::make_circ_mask(5),
      xmn = -5, xmx = 5, ymn = -5, ymx = 5), add = TRUE, legend = FALSE)

 # test with real data
 poi <- c(152, -27)
 aoi <- slga:::validate_poi(poi = poi, product = 'SLPPC', buff = 5)
 slope <- get_lscape_data('SLPPC', aoi)
 plot(slope)
 masker <- raster(slope)
 masker[] <- slga:::make_circ_mask(5)
 slope <- slope + masker
 plot(slope)
 plot(sf::st_point(poi), add = TRUE, pch = 19, col = 'red')
 # note: if sf_use_s2 = TRUE, this buffer distance will be Small.
 plot(sf::st_buffer(sf::st_centroid(sf::st_as_sfc(aoi)),
      0.000833 * 5), add = TRUE)

 

slga documentation built on June 12, 2021, 9:07 a.m.