diff --git a/sclin/src/Lib.scala b/sclin/src/Lib.scala
index bfcbb90..f3c91fd 100644
--- a/sclin/src/Lib.scala
+++ b/sclin/src/Lib.scala
@@ -2129,6 +2129,8 @@ extension (env: ENV)
     ```
      */
     case "group" => group
+    // TODO: docs
+    case "~group" => ogroup
     /*
     @s a f' -> ARR[_ _]'
     Equivalent to a combination of #{tk*} and #{dp*}.
@@ -3019,6 +3021,8 @@ extension (env: ENV)
 
   def group: ENV =
     env.mod2((x, y) => y.vec1(f => x.groupBy(SIG_2f1(f), SIG_1f1(f)).toMAP))
+  def ogroup: ENV =
+    env.mod2((x, y) => y.vec1(f => x.ogroupBy(SIG_1f1(f)).toOBS))
 
   def span: ENV = env.mod2((x, y) =>
     y.vec1(f =>
diff --git a/sclin/src/Types.scala b/sclin/src/Types.scala
index ed4e9ce..2d24a0f 100644
--- a/sclin/src/Types.scala
+++ b/sclin/src/Types.scala
@@ -905,6 +905,8 @@ enum ANY:
     case MAP(x) =>
       x.groupBy(f.tupled).view.mapValues(_.toMAP).toMap
     case _ => groupBy(g)
+  def ogroupBy(f: ANY => ANY): Observable[ANY] =
+    toOBS.x.groupBy(f).map(a => Vector(a.key, a.toOBS).toARR)
 
   def span(f: ANY => Boolean): (ANY, ANY) = this match
     case Lsy(x) =>