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I've got a grid/raster in R that is represented as centroids of the grid instead of polygons. I am trying to merge that with points.

library(sf)
nc <- st_read(system.file("shape/nc.shp", package="sf"))
grid_10000 <- st_make_grid(nc, cellsize = c(10000, 10000)) %>% 
  st_sf(grid_id = 1:length(.),grid_prop = sample(c("one","two"),length(.),replace=T))
grid_centroids <- st_centroid(grid_50) %>% cbind(st_coordinates(.))
pts <- st_sample(nc, size = 5) %>% st_sf
# I can join the points easily like this
joined <- st_join(pts,grid_10000)

Now without grid_10000, how could I see which point gets which parameter simply based on the centroids. A method that could make a grid from the centroids would be best. The distances are unknown too. And 'sf' solution would be preferred.

  • Your last line, joined <- (pts,grid_10000) isn't valid R - did you mean c(pts, grid_10000)? – Spacedman Aug 19 '18 at 9:10
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Ok, made a workaround, by estimating the distance from two adjacent centroids and joining the centroids with the newly made grid. But still thinking there ought to be an easier way.

grid_new <- st_make_grid(nc, cellsize = 
    c(as.numeric(st_distance(grid_centroids[1:2,])[,1][2]),
    as.numeric(st_distance(grid_centroids[1:2,])[,2][1]))) %>% 
    st_sf(grid_id = 1:length(.))
grid_with_data_from_centroids <- st_join(grid_new,grid_centroids)
joined <- st_join(pts,grid_with_data_from_centroids)

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