updating in place?

If we want to update the marks in place in the DOM rather than throw them away and create a new one on each tick (in the context of the time animations, and later interactions), we can pass the previous node as part of the context (as in the patch below), and use join rather than append.

(And then, why not go further and always pass a g element, on any call to render — that is, independently of whether it's a previously rendered node or a new one just created with create("svg:g", context)? The mark would still be free to ignore it and return something else, of course.)

diff --git a/src/marks/dot.js b/src/marks/dot.js
index e4140b55..3442267f 100644
--- a/src/marks/dot.js
+++ b/src/marks/dot.js
@@ -1,4 +1,4 @@
-import {path, symbolCircle} from "d3";
+import {path, select, symbolCircle} from "d3";
 import {create} from "../context.js";
 import {positive} from "../defined.js";
 import {identity, maybeFrameAnchor, maybeNumberChannel, maybeTuple} from "../options.js";
@@ -55,13 +55,12 @@ export class Dot extends Mark {
     const {x: X, y: Y, r: R, rotate: A, symbol: S} = channels;
     const [cx, cy] = applyFrameAnchor(this, dimensions);
     const circle = this.symbol === symbolCircle;
-    return create("svg:g", context)
+    return (context.node ? select(context.node) : create("svg:g", context)
         .call(applyIndirectStyles, this, scales, dimensions)
-        .call(applyTransform, this, scales)
-        .call(g => g.selectAll()
+        .call(applyTransform, this, scales))
+        .call(g => g.selectAll(circle ? "circle" : "path")
           .data(index, i => i)
-          .enter()
-          .append(circle ? "circle" : "path")
+          .join(circle ? "circle" : "path")
             .call(applyDirectStyles, this)
             .call(circle
               ? selection => {
diff --git a/src/plot.js b/src/plot.js
index 51864c40..6a9ec847 100644
--- a/src/plot.js
+++ b/src/plot.js
@@ -376,7 +376,7 @@ export function plot(options = {}) {
           }
           const ifacet = [...facet.filter(i => T[i] < time1), ...(currentTime < time1) ? Ii : [], ...facet.filter(i => T[i] >= time1)];
           const index = mark.timeFilter(ifacet, T, currentTime);
-          timeNode = mark.render(index, scales, interp, dimensions, context);
+          timeNode = mark.render(index, scales, interp, dimensions, {...context, node: timeMark.node});
         } else {
           // here typically t = 0;
           const index = mark.timeFilter(facet, T, currentTime);

Review the proposed changes in src/marks/dot.js and src/plot.js, focusing on passing context.node into mark.render and using selection.join. Compare the two suggested behaviors—reusing the previous node or always providing a g element—and clarify which render contract should be adopted. Done means the chosen behavior is implemented consistently for time animations and later interactions.