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14 lines
752 B
JavaScript
14 lines
752 B
JavaScript
export const createStreamVisualizer = async (stream, { maxPoints, alpha, width, height, yDomain }) => {
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const { scaleLinear, line } = await import('https://cdn.jsdelivr.net/npm/d3@7/+esm')
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let data = [], ema
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for await (const { timestamp: t, value: v } of stream) {
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ema = ema === undefined ? v : alpha * v + (1 - alpha) * ema
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data.push({ timestamp: t, value: v, ema })
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if (data.length > maxPoints) data.shift()
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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 { data, path: line().x(d => x(d.timestamp)).y(d => y(d.ema))(data) }
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}
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export default createStreamVisualizer; |