Dynamically filter pmtiles and plot with maplibre in R

pmtiles-filter.R

library(mapgl)
library(dplyr)
library(duckdbfs)

# This test file demonstrates that given a SQL query on the parquet version
# of the data, we can identify all the features included in the response and
# construct a maplibre filter that filters the corresponding features in 
# the pmtiles vesion.

pmtiles <- "https://data.source.coop/cboettig/social-vulnerability/svi2020_us_tract.pmtiles"
parquet <- "https://data.source.coop/cboettig/social-vulnerability/svi2020_us_tract.parquet"
svi <- open_dataset(parquet, tblname = "svi")

response = list(query = 
"SELECT STATE, AVG(RPL_THEMES) as avg_social_vulnerability
FROM svi GROUP BY STATE, ORDER BY avg_social_vulnerability
DESC LIMIT 1")

con <- duckdbfs::cached_connection()
df <- DBI::dbGetQuery(con, response$query)

filter_column <- function(full_data, filtered_data, id_col) {
  values <- full_data |>
    inner_join(filtered_data, copy=TRUE) |>
    pull(id_col)
  # maplibre syntax for the filter of PMTiles  
  list("in", list("get", id_col), list("literal", values))
}

maplibre(center = c(-102.9, 41.3), zoom = 3) |>
    add_fill_layer(
        id = "svi_layer",
        source = list(type = "vector", url  = paste0("pmtiles://", pmtiles)),
        source_layer = "SVI2000_US_tract",
        filter = filter_column(svi, df, "FIPS"),
        fill_opacity = 0.5,
        fill_color = interpolate(column = "RPL_THEMES",
                                values = c(0, 1),
                                stops = c("lightblue", "darkblue"),
                                na_color = "lightgrey")
    )