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