The avatar for @observablehq
Observable
The end-to-end solution for building and hosting better data apps, dashboards, and reports.
Public
Data Analysis
Edited
Nov 15, 2022
Importers
10 stars
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
timeWindow = d3.timeFormat('%A')
Insert cell
Insert cell
timeWindow(new Date)
Insert cell
Insert cell
seasonallyAdjustedMTA = seasonalityIndex(sampleData, "Value", "Date", timeWindow)
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
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
}
});
}
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell

Purpose-built for displays of data

Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
Learn more