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27 lines
760 B
JavaScript
27 lines
760 B
JavaScript
const createStreamVisualizer = async (feed, { maxPoints: max, alpha, width, height, yDomain }) => {
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const d3 = await import('https://esm.sh/d3');
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let data = [], ema;
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for await (const { timestamp, value } of feed) {
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ema = ema == null ? value : alpha * value + (1 - alpha) * ema;
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data.push({ timestamp, value, ema });
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if (data.length > max) data.shift();
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}
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if (!data.length) return { data, path: "" };
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const x = d3.scaleLinear()
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.domain([data[0].timestamp, data.at(-1).timestamp])
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.range([0, width]);
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const y = d3.scaleLinear()
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.domain(yDomain)
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.range([height, 0]);
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const path = d3.line()
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.x(d => x(d.timestamp))
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.y(d => y(d.ema))(data);
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return { data, path };
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};
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export default createStreamVisualizer; |