add plotObservable shorthand function

CHANGELOG.md

@@ -1,6 +1,12 @@
 CHANGELOG
 ===
 
+# 3.1.0
+
+> 2023-04-29
+
+Add the `plotObservable` function as a shorthand for using Observablehq/plot charts.
+
 # 3.0.0
 
 > 2023-04-07

src/plotObservable.js

@@ -0,0 +1,15 @@
+import plot from './plot.js';
+
+/**
+ * Plot Vega charts
+ * @param {Object} [chartConfig] An @observablehq/plot function
+ * @param {String} [options] Options
+ * @param {String} [options.outPath=''] A filepath to write the image.
+ * @param {Boolean} [options.view=true] If true, show the chart in a popup window.
+ * @param {String} [options.css] Any CSS that you want injected into the page to tweak styles.
+ * @param {String} [options.title='Chart'] If `view` is true, add a title to the window's page. A timestamp will be appended to this.
+ * @param {Boolean} [options.debug] Whether to run the screenshot browser in headfull mode.
+ */
+export default async function plotObservable(chartConfig, data, options = {}) {
+	await plot(chartConfig, [data], { ...options, library: 'observablehq/plot' });
+}

test/plotObservable.test.js

@@ -0,0 +1,38 @@
+/* eslint-disable no-undef */
+import { readDataSync } from 'indian-ocean';
+import * as aq from 'arquero';
+
+import plotObservable from '../src/plotObservable.js';
+
+const events = readDataSync('./test/data/purchase_data.csv');
+
+const dataset = aq
+	.from(events)
+	.derive({ date: aq.escape(d => new Date(d.date.split('T')[0])) })
+	.groupby('date', 'brand')
+	.rollup({ value: d => aq.op.sum(d.price_in_usd) })
+	.orderby('date', 'brand')
+	.objects();
+
+const chart = data => Plot.plot({
+	marks: [
+		Plot.line(data, {
+			x: 'date',
+			y: 'value',
+			stroke: 'brand',
+			strokeWidth: 2,
+			curve: 'linear'
+		})
+	],
+	width: 554,
+	height: 130,
+	x: { ticks: 3 },
+	marginLeft: 50,
+	color: {
+		legend: true,
+		width: 554,
+		columns: '120px'
+	}
+});
+
+await plotObservable(chart, dataset);