use CMHC data portal spatial features to inform CT translation data

data-raw/cmhc_ct_translation_data.R

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+# Rebuild cmhc_ct_translation_data from two sources:
+# 1. CMHC geospatial API — CT-level geography with METCODE, neighbourhoods, zones
+# 2. cancensus (CA21) — authoritative CT → CSD mapping
+
+# --- 1. Fetch all CT records from CMHC's ArcGIS REST service ---
+url <- paste0(
+  "https://geospatial.cmhc-schl.gc.ca/server/rest/services/",
+  "CMHC_APPS/HMIP_CURRENT_CAWD/MapServer/0/query"
+)
+res <- httr::GET(
+  url,
+  query = list(
+    where = "1=1",
+    outFields = "*",
+    returnGeometry = "false",
+    f = "json",
+    resultRecordCount = 10000
+  )
+)
+raw_json <- jsonlite::fromJSON(httr::content(res, "text"), flatten = TRUE)
+raw <- tibble::as_tibble(raw_json$features)
+names(raw) <- sub("^attributes\\.", "", names(raw))
+
+# --- 2. Build translation table ---
+rebuild <- dplyr::transmute(
+  raw,
+  CTUID = paste0(sgc_cma_ca_cde, sgc_census_tract_cde),
+  CMHC_CT = sgc_census_tract_cde,
+  CMHCCT_UID = paste0(metropolitan_major_area_cde, sgc_census_tract_cde),
+  CSDUID = NA_character_,
+  METCODE = metropolitan_major_area_cde,
+  METNAME_EN = metropolitan_major_area_current_nm,
+  METNBHD = paste0(
+    metropolitan_major_area_cde,
+    stringr::str_pad(neighbourhood_cde, width = 3, pad = "0")
+  ),
+  NBHDCODE = neighbourhood_cde,
+  NBHDNAME_EN = neighbourhood_current_nm_en,
+  NBHDNAME_LONG_EN = neighbourhood_current_nm_en,
+  ZONECODE = survey_zone_cde,
+  ZONENAME_EN = survey_zone_current_nm_en,
+  ZONENAME_LONG_EN = survey_zone_current_nm_en,
+  CATEGORY_EN = "MET",
+  NAME_EN = sgc_census_tract_cde
+)
+
+# --- 3. Join CSDUID from cancensus (authoritative CT → CSD mapping) ---
+ct_cancensus <- cancensus::get_census(
+  "CA21",
+  regions = list(C = "01"),
+  level = "CT"
+)
+csd_lookup <- ct_cancensus[, c("GeoUID", "CSD_UID")]
+rebuild <- dplyr::left_join(rebuild, csd_lookup, by = c("CTUID" = "GeoUID"))
+rebuild$CSDUID <- rebuild$CSD_UID
+rebuild$CSD_UID <- NULL
+
+# --- 4. Filter out CMHC-only CTs ---
+# The CMHC API returns ~300 CTs that are CMHC-specific subdivisions with no
+# corresponding StatCan census tract (e.g., CMHC splits Ile d'Orleans near
+# Quebec City into 6 CTs while StatCan defines just 1). They return no
+# data on the CMHC portal or the ExportTable endpoint, and have no census
+# GeoUID, so they cannot be used with cmhc_geo_uid_for_census(). We exclude
+# them by keeping only rows that matched a cancensus CT.
+rebuild <- rebuild[!is.na(rebuild$CSDUID), ]
+
+# --- 5. Save ---
+cmhc_ct_translation_data <- rebuild
+usethis::use_data(cmhc_ct_translation_data, overwrite = TRUE)