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20 lines
892 B
JavaScript
20 lines
892 B
JavaScript
const createStreamVisualizer = async (src, opt = {}) => {
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const { maxPoints = 100, alpha = 0.5, width = 600, height = 300, yDomain = [0, 1] } = opt
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const { scaleLinear, line } = await import('https://cdn.jsdelivr.net/npm/d3@7/+esm')
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const data = []
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let ema
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for await (const p of src) {
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if (!p) continue
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const { timestamp: t, value: v } = p
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if (t == null || v == null) continue
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ema = ema == null ? v : alpha * v + (1 - alpha) * ema
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data.push({ timestamp: t, value: v, ema })
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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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const path = line().x(d => x(d.timestamp)).y(d => y(d.ema))(data) || ''
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return { data, path }
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}
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export default createStreamVisualizer; |