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<!DOCTYPE html> |
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<meta charset="utf-8"> |
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<style> |
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/* look in the inspector for what axis--x refers to */ |
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.axis--x path { |
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/* changing this affects whether the x-axis is drawn */ |
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display: none; |
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} |
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.line { |
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/* try changing the fill---notice how weird it looks! */ |
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/* that is because we do not have closed polygons. */ |
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fill: none; |
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stroke: steelblue; |
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/* you can slide this value back and forth to see which lines are impacted */ |
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stroke-width: 1.5px; |
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} |
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/* lets make our svg area more visible */ |
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body { |
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background-color: black; |
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margin: 0px; |
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} |
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svg { |
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background-color: whitesmoke; |
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} |
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/* make it really clear where the plot area is inside the svg */ |
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rect#plot { |
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fill: white; |
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stroke: none; |
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} |
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</style> |
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<svg width="960" height="500"></svg> |
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<script src="//d3js.org/d3.v4.min.js"></script> |
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<script> |
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var svg = d3.select("svg"), |
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margin = {top: 20, right: 80, bottom: 30, left: 50}, |
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width = svg.attr("width") - margin.left - margin.right, |
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height = svg.attr("height") - margin.top - margin.bottom, |
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g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")"); |
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// make it really clear where the plot area is inside the svg |
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g.append("rect") |
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.attr("id", "plot") |
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.attr("x", 0) |
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.attr("y", 0) |
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.attr("width", width) |
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.attr("height", height); |
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var parseTime = d3.timeParse("%Y%m%d"); |
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// what is parseTime? use the console! |
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// console.log(parseTime); |
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// console.log(typeof parseTime); |
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// console.log(parseTime("20160207")); |
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var x = d3.scaleTime().range([0, width]), |
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y = d3.scaleLinear().range([height, 0]), |
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z = d3.scaleOrdinal(d3.schemeCategory10); |
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// of course d3 has a built-in time scale! |
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// this makes our lives easier if we have date objects |
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// note the scales here do not have domains set |
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// that will happen when the data is loaded |
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// https://github.com/d3/d3-shape#lines |
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var line = d3.line() |
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.curve(d3.curveBasis) |
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.x(function(d) { return x(d.date); }) |
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.y(function(d) { return y(d.temperature); }); |
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// we have another function here! |
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// console.log(typeof line); |
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// it will help us draw lines from our data |
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// the x() and y() calls have accessor functions defined |
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// these tell d3 what to use in our data for x-position and y-position |
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// try changing the "curve" type to: |
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// curveCardinal, curveCatmullRom, curveLinear, curveNatural, curveStep |
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// https://github.com/d3/d3-shape#curves |
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// line.curve(d3.curveStep); |
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// remember data is loaded asynchronously! |
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// https://github.com/d3/d3-request/blob/master/README.md#tsv |
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// console.log("before d3.tsv()"); |
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// the type parameter is a row accessor function (see below) |
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d3.tsv("data.tsv", type, function(error, data) { |
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if (error) throw error; |
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// console.log("inside d3.tsv()"); |
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// whoa, what? |
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var cities = data.columns.slice(1).map(function(id) { |
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return { |
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id: id, |
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values: data.map(function(d) { |
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return {date: d.date, temperature: d[id]}; |
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}) |
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}; |
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}); |
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// if we log this, note we get objects |
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// each object has an "id" and "values" |
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// console.log(cities); |
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// compare that to data |
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// console.log(data); |
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// our data has several properties |
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// console.log(data.columns); |
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// console.log(data.length); |
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// slice is built into javascript |
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice |
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// console.log(data.columns.slice(1)); |
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// map is also built into javascript |
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map |
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// console.log(data.columns.slice(1).map(function(potato) { return potato.toUpperCase(); })); |
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// console.log(data.columns.slice(1).map(function(potato) { return {"id": potato}; })); |
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// so what is the second data.map() call doing? |
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// console.log(data); |
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// console.log(data.map(function(orange) { return orange["New York"];})); |
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// now that our data is in a useful format |
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// we can set our domains for our scales |
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// https://github.com/d3/d3-array#extent |
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x.domain(d3.extent(data, function(d) { return d.date; })); |
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// https://github.com/d3/d3-array#min |
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// have to calculate min for each city first (min of NY, min of SF, etc.) |
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// then calculate the min of the three city minimums |
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// console.log(d3.min(cities[0].values, function(d) { return d.temperature; })); |
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// console.log(d3.min(cities[1].values, function(d) { return d.temperature; })); |
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// console.log(d3.min(cities[2].values, function(d) { return d.temperature; })); |
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y.domain([ |
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d3.min(cities, function(c) { return d3.min(c.values, function(d) { return d.temperature; }); }), |
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d3.max(cities, function(c) { return d3.max(c.values, function(d) { return d.temperature; }); }) |
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]); |
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// this maps our city names to colors |
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z.domain(cities.map(function(c) { return c.id; })); |
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// console.log(z("New York")); |
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// we can finally draw our axis lines |
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g.append("g") |
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.attr("class", "axis axis--x") |
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.attr("transform", "translate(0," + height + ")") |
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.call(d3.axisBottom(x)); |
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g.append("g") |
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.attr("class", "axis axis--y") |
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.call(d3.axisLeft(y)) |
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// ooo fancy text stuff so we can label our axis! |
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.append("text") |
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// we have seen translate transforms already |
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// we can also rotate, but this form rotates around 0,0 |
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.attr("transform", "rotate(-90)") |
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.attr("y", 6) |
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.attr("dy", "0.71em") |
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.attr("fill", "#000") |
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.text("Temperature, ºF"); |
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// okay now we create a group per city |
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// verify this in the elements view! |
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var city = g.selectAll(".city") |
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.data(cities) |
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.enter().append("g") |
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.attr("class", "city"); |
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// need this if we want to add marks |
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// line.curve(d3.curveLinear); |
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// create one line per city using our generator |
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city.append("path") |
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.attr("class", "line") |
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.attr("d", function(d) { return line(d.values); }) |
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.style("stroke", function(d) { return z(d.id); }); |
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// more fancy text code! |
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// this places city names at the end of the lines |
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city.append("text") |
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// datum() is different from data() |
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// https://github.com/d3/d3-selection/blob/master/README.md#selection_datum |
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// it does not create enter/update/exit selections |
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// our "data" is each city name and the *last* value |
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.datum(function(d) { return {id: d.id, value: d.values[d.values.length - 1]}; }) |
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// we will shift our label text based on the last date and last temperature value |
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.attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.temperature) + ")"; }) |
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.attr("x", 3) |
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.attr("dy", "0.35em") |
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.style("font", "10px sans-serif") |
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.text(function(d) { return d.id; }); |
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// so, can we add line markers to this easily? |
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// we needed once line per city before |
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// but now we need several circles per city |
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// how do we do that? |
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/* |
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var marks = city.append("g") |
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.style("stroke", function(d) { return z(d.id); }) |
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.selectAll("circle") |
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.data(function(d) { return d.values; }) |
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.enter() |
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.append("circle") |
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.attr("cx", function(d) { return x(d.date); }) |
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.attr("cy", function(d) { return y(d.temperature); }) |
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.attr("r", 3) |
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.style("fill", "white"); |
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*/ |
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// okay so that looks terrible but you get the idea |
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}); |
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// console.log("after d3.tsv()"); |
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// this is our row accessor function |
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// it tells d3 how to convert our data for every row |
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function type(d, _, columns) { |
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// console.log(d, columns); |
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// we need to convert the date string to a date object |
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d.date = parseTime(d.date); |
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// mmm, a one-line for loop... lets break this down |
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for (var i = 1, n = columns.length, c; i < n; ++i) d[c = columns[i]] = +d[c]; |
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// first three variables are declared (i, n, and c) |
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// only i and n are initialized |
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// the loop continues until i < n and increments i each loop |
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// inside the loop we are setting c = columns[i] which is the city name |
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// this is the "property" of the object |
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// and we are just making sure the value is converted from a string to a number |
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// so the one line above is equivalent to: |
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// var n = columns.length; |
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// var c; |
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// for (var i = 1; i < n; ++i) { |
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// c = columns[i]; |
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// d[c] = +d[c]; |
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// } |
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return d; |
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} |
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</script> |