breadth-first type inference

src/scales.js

@@ -76,31 +76,35 @@ function inferScaleType(key, channels, {type, domain, range}) {
   }
   if (registry.get(key) === radius) return "sqrt";
   for (const {type} of channels) if (type !== undefined) return type;
-  if ((domain || range || []).length > 2) return inferOrdinalType(key);
+  if ((domain || range || []).length > 2) return asOrdinalType(key);
   if (domain !== undefined) {
-    type = inferScaleTypeFromValues(key, domain);
-    if (type !== undefined) return type;
-  }
-  channels = channels.filter(({value}) => value !== undefined);
-  if (!channels.length) return;
-  for (const {value} of channels) {
-    type = inferScaleTypeFromValues(key, value);
-    if (type !== undefined) return type;
+    if (isOrdinal(domain)) return asOrdinalType(key);
+    if (isTemporal(domain)) return "utc";
+    return "linear";
   }
+  // If any channel is ordinal or temporal, it takes priority.
+  const values = channels.map(({value}) => value).filter(value => value !== undefined);
+  if (values.some(isOrdinal)) return asOrdinalType(key);
+  if (values.some(isTemporal)) return "utc";
   return "linear";
 }
 
-function inferScaleTypeFromValues(key, values) {
+function isOrdinal(values) {
   for (const value of values) {
     if (value == null) continue;
-    if (typeof value === "string") return inferOrdinalType(key);
-    if (typeof value === "boolean") return inferOrdinalType(key);
-    if (value instanceof Date) return "utc";
-    return "linear";
+    const type = typeof value;
+    return type === "string" || type === "boolean";
+  }
+}
+
+function isTemporal(values) {
+  for (const value of values) {
+    if (value == null) continue;
+    return value instanceof Date;
   }
 }
 
 // Positional scales default to a point scale instead of an ordinal scale.
-function inferOrdinalType(key) {
+function asOrdinalType(key) {
   return registry.get(key) === position ? "point" : "ordinal";
 }

test/plots/index.js

@@ -10,8 +10,8 @@ export {default as carsParcoords} from "./cars-parcoords.js";
 export {default as covidIhmeProjectedDeaths} from "./covid-ihme-projected-deaths.js";
 export {default as d3Survey2015Comfort} from "./d3-survey-2015-comfort.js";
 export {default as d3Survey2015Why} from "./d3-survey-2015-why.js";
-export {default as diamondsCaratPriceDots} from "./diamonds-carat-price-dots.js";
 export {default as diamondsCaratPrice} from "./diamonds-carat-price.js";
+export {default as diamondsCaratPriceDots} from "./diamonds-carat-price-dots.js";
 export {default as empty} from "./empty.js";
 export {default as gistempAnomaly} from "./gistemp-anomaly.js";
 export {default as gistempAnomalyMoving} from "./gistemp-anomaly-moving.js";
@@ -25,26 +25,27 @@ export {default as letterFrequencyBar} from "./letter-frequency-bar.js";
 export {default as letterFrequencyColumn} from "./letter-frequency-column.js";
 export {default as letterFrequencyDot} from "./letter-frequency-dot.js";
 export {default as letterFrequencyLollipop} from "./letter-frequency-lollipop.js";
-export {default as metroInequalityChange} from "./metro-inequality-change.js";
 export {default as metroInequality} from "./metro-inequality.js";
-export {default as metroUnemploymentIndex} from "./metro-unemployment-index.js";
+export {default as metroInequalityChange} from "./metro-inequality-change.js";
+export {default as metroUnemployment} from "./metro-unemployment.js";
 export {default as metroUnemploymentHighlight} from "./metro-unemployment-highlight.js";
+export {default as metroUnemploymentIndex} from "./metro-unemployment-index.js";
 export {default as metroUnemploymentMoving} from "./metro-unemployment-moving.js";
 export {default as metroUnemploymentNormalize} from "./metro-unemployment-normalize.js";
 export {default as metroUnemploymentRidgeline} from "./metro-unemployment-ridgeline.js";
-export {default as metroUnemployment} from "./metro-unemployment.js";
 export {default as mobyDickFaceted} from "./moby-dick-faceted.js";
 export {default as mobyDickLetterFrequency} from "./moby-dick-letter-frequency.js";
 export {default as mobyDickLetterPosition} from "./moby-dick-letter-position.js";
 export {default as morleyBoxplot} from "./morley-boxplot.js";
 export {default as moviesProfitByGenre} from "./movies-profit-by-genre.js";
 export {default as musicRevenue} from "./music-revenue.js";
+export {default as ordinalBar} from "./ordinal-bar.js";
 export {default as penguinCulmen} from "./penguin-culmen.js";
 export {default as penguinCulmenArray} from "./penguin-culmen-array.js";
-export {default as penguinMassSexSpecies} from "./penguin-mass-sex-species.js";
+export {default as penguinMass} from "./penguin-mass.js";
 export {default as penguinMassSex} from "./penguin-mass-sex.js";
+export {default as penguinMassSexSpecies} from "./penguin-mass-sex-species.js";
 export {default as penguinMassSpecies} from "./penguin-mass-species.js";
-export {default as penguinMass} from "./penguin-mass.js";
 export {default as penguinSexMassCulmenSpecies} from "./penguin-sex-mass-culmen-species.js";
 export {default as penguinSpeciesIsland} from "./penguin-species-island.js";
 export {default as policeDeaths} from "./police-deaths.js";

test/plots/ordinal-bar.js

@@ -0,0 +1,13 @@
+import * as Plot from "@observablehq/plot";
+
+export default async function() {
+  return Plot.plot({
+    y: {
+      grid: true
+    },
+    marks: [
+      Plot.barY("ABCDEF", {x: (d, i) => i}),
+      Plot.ruleY([0])
+    ]
+  });
+}