S18 - HW 3 - Bar Chart

CS 725/825 - Spring 2018 - Homework 3 - Bar Chart

Varsha Ravi-01067335

This simple bar chart is constructed from a TSV file storing the frequency of letters in the English language.

Type of mark used - Lines (Thick lines)
List of channels - Length,Position
Attributes they are mapped to - Position of y axis of Quantitative, Position of x axis of Categorical
Data type - Frequency dimension, Alphabet

Graph 1 - In graph 1 Color hue was applied to get different colors for each alphabet. This could be obtained using colorScale = d3.scaleOrdinal(d3.schemeCategory20); , but this provides only 20 set of colors and the colors will be repeated for the next 6 colors as the loop repeats. Thus the data set has been called using .domain and then using range 26 different colors have been assigned.

Channels - Length, position, color hue
Attributes they are mapped to - Position of x axis(Letters) of Quantitative, Position of y axis(frequency) of Categorical
Data types - Frequency dimension, Alphabet

Graph 2 - In Graph 2 color saturation was applied to get saturation of clors from darker shade to lighter shade to the highest to lowest frequency respectively.

Channels - Length, position, color saturation
Attributes they are mapped to - Position of x axis(Letters) of Quantitative, Position of y(frequency) axis of Categorical
Data types - Frequency dimension, Alphabet

References:

https://github.com/d3/d3-scale
https://www.dashingd3js.com/d3js-scales
https://bl.ocks.org/pstuffa/3393ff2711a53975040077b7453781a9

<!DOCTYPE html>
<html>
<meta charset="utf-8">
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script>

<body>
	<p>Frequency of usage of letters in English</p>
	<h2>Bar Chart 1</h2>
  <div><svg id="chart1" width="800" height="400"></svg></div>
	<h2>Bar Chart 2</h2>
  <div><svg id="chart2" width="800" height="400"></svg></div>

// See https://github.com/d3/d3-scale
var x1 = d3.scaleBand().rangeRound([0, width]).padding(0.1),
    y1 = d3.scaleLinear().rangeRound([height, 0]); // note that we've reversed the range

// creates new svg <g> space, sets new (0,0) at left, top margin
var g1 = svg1.append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.tsv("data.tsv", function(d) {
  d.frequency = +d.frequency;    // convert text to number
  return d;
}, function(error, data) {
  if (error) throw error;

var colorScale = d3.scaleOrdinal()
					.domain([data.letter])  
		.range(['#8B4513','#ff4759','#FF0000','#0000FF','#dbdb00','#00FFFF','#FF00FF','#C0C0C0','#808080','#470000','#808000','#800080','#008080','#000080','	#8B0000	','#FF8C00','#808000','#00FA9A','#3CB371','#4682B4','	#8B008B','#FF69B4','#D2691E','#708090','#DA70D6','#40E0D0']);
  
//colorScale = d3.scaleOrdinal(d3.schemeCategory20);
  
  // See https://www.dashingd3js.com/d3js-scales
  // maps domain of x values (letters) to range of positions on x-axis
  x1.domain(data.map(function(d) { return d.letter; }));  
  // maps domain of y values (frequencies 0, max freq) to range of positions on y-axis
  y1.domain([0, d3.max(data, function(d) { return d.frequency; })]);

// x-axis
  g1.append("g")
    .attr("class", "axis x-axis")
    .attr("transform", "translate(0," + height + ")") // move axis to bottom of chart
    .call(d3.axisBottom(x1));
  
  // y-axis
  g1.append("g")
    .attr("class", "axis y-axis")
    .call(d3.axisLeft(y1).ticks(10, "#")); // number of ticks and type

// y-axis label
  g1.append("text")
  	.attr("class", "label")
    .attr("x", 0-margin.left)       // set x position of label
    .attr("y", 0-margin.top/2)			// set y position of label
    .style("text-anchor", "start")  // left-justify
  	.text ("Frequency")
  
  // bars
  g1.selectAll(".bar")
    .data(data)
    .enter().append("rect")
      .attr("class", "bar")
      .attr("x", function(d) { console.log ("letter: " + d.letter + ", x: " + x1(d.letter)); return x1(d.letter); })
      .attr("y", function(d) { console.log ("freq: " + d.frequency + ", y: " + y1(d.frequency)); return y1(d.frequency); })
      .attr("width", x1.bandwidth()) // width of each band 
      .attr("height", function(d) { return height - y1(d.frequency); })
  		.style("fill", function(d)
            {return colorScale(d.letter);})  // color of the bars
  ;
});
  
// chart 2  
var svg2 = d3.select("#chart2"),
    margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = +svg2.attr("width") - margin.left - margin.right,
    height = +svg2.attr("height") - margin.top - margin.bottom;

var x2 = d3.scaleBand().rangeRound([0, width]).padding(0.1),
    y2 = d3.scaleLinear().rangeRound([height, 0]);

var g2 = svg2.append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// x-axis
  g2.append("g")
    .attr("class", "axis axis--x")
    .attr("transform", "translate(0," + height + ")") 
    .call(d3.axisBottom(x2));

// y-axis
  g2.append("g")
    .attr("class", "axis axis--y")
    .call(d3.axisLeft(y2).ticks(10, "#"));

// y-axis label
  g2.append("text")
  	.attr("class", "label")
    .attr("x", 0-margin.left)
    .attr("y", 0-margin.top/2)
    .style("text-anchor", "begin")
  	.text ("Frequency")
  
  // bars
  g2.selectAll(".bar")
    .data(data)
    .enter().append("rect")
      .attr("class", "bar")
      .attr("x", function(d) { return x2(d.letter); })
      .attr("y", function(d) { return y2(d.frequency); })
      .attr("width", x2.bandwidth())
      .attr("height", function(d) { return height - y2(d.frequency); })
  		.style("fill", function(d)
            {return color(d.frequency);})  // color of the bars
  ;
});
</script>
</body>
</html>

https://d3js.org/d3.v4.min.js

https://d3js.org/d3-scale-chromatic.v1.min.js