Add filter_gisjoin function

DESCRIPTION

@@ -29,9 +29,11 @@ Suggests:
     sf,
     tibble,
     tidyr,
-    tigris,
+    tigris (>= 2.1.1),
     withr
 Encoding: UTF-8
 LazyData: true
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.3.1
+Remotes:  
+    elipousson/tigris

R/filter_gisjoin.R

@@ -0,0 +1,27 @@
+#' Filter a NHGIS data frame by a state FIPS and county FIPS numbers
+#'
+#' By default, filter to counties in the Baltimore metro area.
+#'
+#' @param values Optional vector of GISJOIN values. state_fips and county_fips
+#'   are ignored if this is supplied.
+#' @keywords internal
+filter_gisjoin <- function(data,
+                           state = NULL,
+                           county = NULL,
+                           values = NULL,
+                           gisjoin_col = "GISJOIN") {
+  if (is.null(values)) {
+    check_installed("tigris")
+
+    if (!is.null(state) && is.null(county)) {
+      state <- tigris:::validate_state(state = state, multiple = TRUE)
+      values <- paste0("G", state_fips, "0")
+    } else {
+      state <- tigris:::validate_state(state = state)
+      county <- tigris:::validate_state(state = state, county = county, multiple = TRUE)
+      values <- paste0("G", state, "0", county, "0")
+    }
+  }
+
+  dplyr::filter(data, .data[[gisjoin_col]] %in% values)
+}