scope rng for repeatable output

Author: mbostock

test/plots/identity-scale.js

@@ -1,9 +1,8 @@
 import * as Plot from "@observablehq/plot";
 import * as d3 from "d3";
 
-const random = d3.randomLcg(42);
-
 export default async function() {
+  const random = d3.randomLcg(42);
   return Plot.plot({
     x: {
       type: "identity"

test/plots/random-walk.js

@@ -1,9 +1,8 @@
 import * as Plot from "@observablehq/plot";
 import * as d3 from "d3";
 
-const randomNormal = d3.randomNormal.source(d3.randomLcg(42))();
-
 export default async function() {
+  const randomNormal = d3.randomNormal.source(d3.randomLcg(42))();
   return Plot.plot({
     marks: [
       Plot.lineY(d3.cumsum({length: 500}, randomNormal), {stroke: "red"}),

test/plots/uniform-random-difference.js

@@ -1,9 +1,8 @@
 import * as Plot from "@observablehq/plot";
 import * as d3 from "d3";
 
-const random = d3.randomLcg(42);
-
 export default async function() {
+  const random = d3.randomLcg(42);
   return Plot.plot({
     x: {
       label: "Difference of two uniform random variables",