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Public
Data Analysis
Edited
Nov 15, 2022
Importers
10 stars
Data Analysis
Data wrangling essentials: comparisons in JavaScript, Python, SQL, R, and ExcelMethods of Comparison, Compared
Seasonality Index
Correlation over timeDescriptive statistics: comparisons in JavaScript, Python, SQL, R, and ExcelDiscovering Date PatternsSeasonal SpiralsMonthly Retail Trade ReportPizza ParadiseHacking Power BI Charts with PlotSQL Mystery GameShark Tank: Tech Pitches ExplorationWatch the NBA Finals Players Data Jam on Observable
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timeWindow = d3.timeFormat('%A')
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timeWindow(new Date)
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seasonallyAdjustedMTA = seasonalityIndex(sampleData, "Value", "Date", timeWindow)
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seasonalityIndex = (data, valueKey, dateKey, seasonalityDateFormat) => {
/*
seasonalityDateFormat supports d3.utcFormat or d3.timeFormats
*/
const distinctUnits = Array.from(new Set(data.map(d => d[dateKey]).map(d => seasonalityDateFormat(d))));
const unitMeans = d3.rollup(data, v => d3.mean(v, d => d[valueKey]), d => seasonalityDateFormat(d[dateKey]));
const overallAverage = d3.mean(Array.from(unitMeans), d => d[1]);
const unitSeasonalityIndex = d3.rollup(unitMeans, v => v[0][1] / overallAverage, d => d[0]);

return data.map(d => {
const unit = seasonalityDateFormat(d[dateKey])
const index = unitSeasonalityIndex.get(unit)
return {
...d,
seasonality: d[valueKey] / index
}
});
}
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