md`# Extracting Data from CSV`
d3 = require("d3@5")
topojson = require("topojson-client@3")
states = FileAttachment("states.json").json()
states_features = topojson.feature(states, states.objects.states)
csv_data = d3.csvParse(await FileAttachment("iowa_counties.csv").text(),({FIPS, FEMALES, POP2010}) => [FIPS, [+FEMALES, +FEMALES/+POP2010]])
//this is how to take the values of a variable (column) from all variables you created from the csv file
femalepct = Array.from(csv_data.values(), d => d[1][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: ["Females", "Female Pct"]})
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