[GitHub] [arrow] thisisnic commented on a diff in pull request #35543: GH-35542 : [R] Impement schema extraction function

["thisisnic (via GitHub)" <gi...@apache.org>]

thisisnic commented on code in PR #35543:
URL: https://github.com/apache/arrow/pull/35543#discussion_r1233962048


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r/R/schema.R:
##########
@@ -240,10 +226,48 @@ print_schema_fields <- function(s) {
   paste(map_chr(s$fields, ~ .$ToString()), collapse = "\n")
 }
 
-#' @param ... [fields][field] or field name/[data type][data-type] pairs
+#' Schemas
+#'
+#' Create a schema or extract one from an object.
+#'
+#' @seealso [Schema] for detailed documentation of the Schema R6 object
+#' @param ... [fields][field], field name/[data type][data-type] pairs, or object from which to extract a schema
+#' @examples
+#' # Create schema using pairs of field names and data types
+#' schema(a = int32(), b = float64())
+#'
+#' # Create schema using fields
+#' schema(
+#'   field("b", double()),
+#'   field("c", bool(), nullable = FALSE),
+#'   field("d", string())
+#' )
+#'
+#' # Extract schemas from objects
+#' df <- data.frame(col1 = 2:4, col2 = c(0.1, 0.3, 0.5))
+#' tab1 <- arrow_table(df)
+#' schema(tab1)
+#' tab2 <- arrow_table(df, schema = schema(col1 = int8(), col2 = float32()))
+#' schema(tab2)
+#' @export
+schema <- function(...){
+  UseMethod("schema")
+}
+
 #' @export
-#' @rdname Schema
-schema <- Schema$create
+schema.default <- Schema$create

Review Comment:
   I don't understand this; how can `..object` be missing, but `...` be present?



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