Support average for tables.

crates/nu-cli/tests/commands/average.rs

@@ -0,0 +1,26 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn can_average_numbers() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+             open sgml_description.json
+             | get glossary.GlossDiv.GlossList.GlossEntry.Sections
+             | average
+             | echo $it
+         "#
+    ));
+
+    assert_eq!(actual.out, "101.5")
+}
+
+#[test]
+fn can_average_bytes() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats",
+        "ls | sort-by name | skip 1 | first 2 | get size | average | format \"{$it}\" | echo $it"
+    );
+
+    assert_eq!(actual.out, "1.6 KB");
+}

crates/nu-cli/tests/commands/mod.rs

@@ -1,5 +1,6 @@
 mod alias;
 mod append;
+mod average;
 mod cal;
 mod calc;
 mod cd;