precip cells for USGS-VIZLAB#11

scripts/process/grid_from_mask.R

@@ -0,0 +1,19 @@
+#' take an sf object polygon and make a grid out of it
+#' 
+#' 
+process.grid_from_mask <- function(viz){
+  deps <- readDepends(viz)
+  checkRequired(viz, c("cell_size"))
+
+  clip_poly <- deps[['clip_poly']]
+  crs <- sf::st_crs(clip_poly)
+  cell_size <- viz[["cell_size"]]
+
+  # this is a simple way to dissolve multiple polygons into a single mask
+  clip_mask <- clip_poly %>% 
+    mutate(group=1) %>% group_by(group) %>% summarise()
+  cell_grid <- sf::st_make_grid(clip_mask, cellsize = cell_size, crs = crs)
+  cell_grid_clipped <- sf::st_intersection(cell_grid, clip_mask)
+
+  saveRDS(cell_grid_clipped, file = viz[['location']])
+}

viz.yaml

@@ -73,5 +73,14 @@ fetch:
     scripts: [scripts/fetch/map_data.R , scripts/fetch/utils.R]
     depends: viewbox_limits
 process:
+  - 
+    id: precip_grid
+    location: cache/precip_grid.rds
+    reader: rds
+    cell_size: 80000
+    processor: grid_from_mask
+    scripts: [scripts/process/precip_cells.R]
+    depends: 
+      clip_poly: "state_map_data"
 visualize:
 publish: