md`# My first exercise`
d3 = require("d3@5")
topojson = require("topojson-client@3")
counties = FileAttachment("counties_us_cont_2020_wgs84.json").json()
county_features = topojson.feature(counties, counties.objects.counties_us_cont_2020_wgs84)
csv_data = d3.csvParse(await FileAttachment("assignment1_county_csv@2.csv").text(),({STATE, AREALAND1, AV0AA2020}) => ([STATE, AV0AA2020 / AREALAND1]))
//this is how to take the values of a variable (column) from all variables you created from the csv file
PopulationDensity = Array.from(csv_data.values(), d => d[1])
//this is how you map the id column to the values. We will use this for joining with topojson later.
data = Object.assign(new Map(csv_data), {title: ["States", "Population_Density"]})
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.
