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Reading the D3 Documentation

- [Reading the D3 Documentation](#reading-the-d3-documentation)
- [map() and filter() methods](#map-and-filter-methods)
- [d3 methods](#d3-methods)
- [Programmatic SVGs](#programmatic-svgs)
- [Scaling Data](#scaling-data)
- [Styling with CSS](#styling-with-css)
- [Adding Text to the chart](#adding-text-to-the-chart)
- [Using SVG groups](#using-svg-groups)
  • API Documentation is a great link to bookmark

map() and filter() methods

var data = [123, 52, 46, 30, 4];

const results = data.filter((entry) => {
    return entry > 50;
});

const mapping = data.map((entry) => {
    console.log(entry.key);
    console.log(entry.value);
});

d3 methods

const example = d3.min(data);
console.log(example);		// values returned

const dataLoHiValue = d3.extent(data);	// return min/max as array

var dictMinValue = d3.min(dounts, (d, i) {
	return d.value;
});

Programmatic SVGs

var data = [132,71,337,93,78,43,20,16,30,8,17,21];
let svg = d3.select('body').append('svg')
				.attr('id', 'chart')
				.attr('height', 450)
				.attr('width', 800);

// creating the bars
// vertical bar graph
svg.selectAll('.bar')
	.data(data)
	.enter() 				// enter phase
	.append('rect')
	.attr('class', 'bar') 	// for future selections
	.attr('x', 0)
	.attr('y', (d i) => {
		return i * 20;
	})
	.attr('width', (d, i) => {
    	return d;
    })
    .attr('height', 19);

Scaling Data

  • Creating scaling functions for both x and y.
var data = [132, 71, 337, 93, 78, 43, 20, 16, 30, 8, 17, 21];
let w = 800;
let h = 450;
let x = d3.scale
    .linear()
    .domain([0, d3.max(data)])
    .range([0, w]);
let y = d3.scale
    .linear()
    .domain([0, data.length])
    .range([0, h]);

let svg = d3
    .select('body')
    .append('svg')
    .attr('id', 'chart')
    .attr('height', h)
    .attr('width', w);

// creating the bars
// vertical bar graph
svg
    .selectAll('.bar')
    .data(data)
    .enter() // enter phase
    .append('rect')
    .attr('class', 'bar') // for future selections
    .attr('x', 0)
    .attr('y', (d, i) => {
        return y(i);
    })
    .attr('width', (d, i) => {
        return x(d); // x() does the scaling
    })
    .attr('height', (d, i) => {
        return y(1) - 1;
    });

Styling with CSS

  • Getting rid of the aliasing
.bar {
    fill: purple;
}

Not that attr('class', 'bar') will manually reset the class value, so you can also use .classed('bar', true) - true to add the class, false to remove.

Adding Text to the chart

  • Creating scaling functions for both x and y.
var data = [132, 71, 337, 93, 78, 43, 20, 16, 30, 8, 17, 21];
let w = 800;
let h = 450;
let x = d3.scale
    .linear()
    .domain([0, d3.max(data)])
    .range([0, w]);
let y = d3.scale
    .linear()
    .domain([0, data.length])
    .range([0, h]);

let svg = d3
    .select('body')
    .append('svg')
    .attr('id', 'chart')
    .attr('height', h)
    .attr('width', w);

function plot(params) {
    // creating the bars
    // vertical bar graph
    this.selectAll('.bar')
        .data(params.data)
        .enter() // enter phase
        .append('rect')
        .attr('class', 'bar') // for future selections
        .attr('x', 0)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('width', (d, i) => {
            return x(d); // x() does the scaling
        })
        .attr('height', (d, i) => {
            return y(1) - 1;
        });

    this.selectAll('.bar-label')
        .data(params.data)
        .enter()
        .append('text')
        .classed('bar-label', true)
        .attr('x', (d, i) => {
            return x(d); // use css to change the anchor
        })
        .attr('dx', -4)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('dy', (d, i) => {
            return y(1) / 1.5 + 2;
        })
        .text((d, i) => {
            return d;
        });
}

// first arg will be what is referenced by "this"
plot.call(svg, {
    data: data
});

Using SVG groups

  • SVG groups are like a div that are a convenience element to allow children to be moved and affected together.
var data = [132, 71, 337, 93, 78, 43, 20, 16, 30, 8, 17, 21];
let w = 800;
let h = 450;
let margin = {
    top: 20,
    bottom: 20,
    left: 20,
    right: 20
};

var width = w - margin.left - margin.right;
var height = h - margin.top - margin.bottom;

let x = d3.scale
    .linear()
    .domain([0, d3.max(data)])
    .range([0, width]);
let y = d3.scale
    .linear()
    .domain([0, data.length])
    .range([0, height]);

let svg = d3
    .select('body')
    .append('svg')
    .attr('id', 'chart')
    .attr('height', h)
    .attr('width', w);

let chart = svg
    .append('g')
    .classed('display', true)
    .attr('transform', 'translate(20, 20)');

function plot(params) {
    // creating the bars
    // vertical bar graph
    this.selectAll('.bar')
        .data(params.data)
        .enter() // enter phase
        .append('rect')
        .attr('class', 'bar') // for future selections
        .attr('x', 0)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('width', (d, i) => {
            return x(d); // x() does the scaling
        })
        .attr('height', (d, i) => {
            return y(1) - 1;
        });

    this.selectAll('.bar-label')
        .data(params.data)
        .enter()
        .append('text')
        .classed('bar-label', true)
        .attr('x', (d, i) => {
            return x(d); // use css to change the anchor
        })
        .attr('dx', -4)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('dy', (d, i) => {
            return y(1) / 1.5 + 2;
        })
        .text((d, i) => {
            return d;
        });
}

// first arg will be what is referenced by "this"
plot.call(chart, {
    data: data
});

Section 4: Making a Complex Chart

Working with Arrays of Objects

If working with a dict, we need an accessor function!

var data = [
    { key: 'Glazed', value: 132 },
    { key: 'Jelly', value: 71 },
    { key: 'Holes', value: 337 },
    { key: 'Sprinkles', value: 93 },
    { key: 'Crumb', value: 78 },
    { key: 'Chocolate', value: 43 },
    { key: 'Coconut', value: 20 },
    { key: 'Cream', value: 16 },
    { key: 'Cruller', value: 30 },
    { key: 'Éclair', value: 8 },
    { key: 'Fritter', value: 17 },
    { key: 'Bearclaw', value: 21 }
];

let w = 800;
let h = 450;
let margin = {
    top: 20,
    bottom: 20,
    left: 20,
    right: 20
};

var width = w - margin.left - margin.right;
var height = h - margin.top - margin.bottom;

let x = d3.scale
    .linear()
    .domain([
        0,
        d3.max(data, (d) => {
            return d.value;
        })
    ])
    .range([0, width]);

let y = d3.scale
    .linear()
    .domain([0, data.length])
    .range([0, height]);

let svg = d3
    .select('body')
    .append('svg')
    .attr('width', 800)
    .attr('height', 420)
    .attr('id', 'chart');
let chart = svg
    .append('g')
    .classed('display', true)
    .attr('transform', 'translate(20, 20)');

function plot(params) {
    // creating the bars
    // vertical bar graph
    this.selectAll('.bar')
        .data(params.data)
        .enter() // enter phase
        .append('rect')
        .attr('class', 'bar') // for future selections
        .attr('x', 0)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('width', (d, i) => {
            return x(d.value); // x() does the scaling
        })
        .attr('height', (d, i) => {
            return y(1) - 1;
        });

    this.selectAll('.bar-label')
        .data(params.data)
        .enter()
        .append('text')
        .classed('bar-label', true)
        .attr('x', (d, i) => {
            return x(d.value); // use css to change the anchor
        })
        .attr('dx', -4)
        .attr('y', (d, i) => {
            return y(i);
        })
        .attr('dy', (d, i) => {
            return y(1) / 1.5 + 2;
        })
        .text((d, i) => {
            return d.value;
        });
}

plot.call(chart, {
    data: data
});

Creating an Ordinal Scale

var data = [
	{key: "Glazed",		value: 132},
	{key: "Jelly",		value: 71},
	{key: "Holes",		value: 337},
	{key: "Sprinkles",	value: 93},
	{key: "Crumb",		value: 78},
	{key: "Chocolate",	value: 43},
	{key: "Coconut", 	value: 20},
	{key: "Cream",		value: 16},
	{key: "Cruller", 	value: 30},
	{key: "Éclair", 	value: 8},
	{key: "Fritter", 	value: 17},
	{key: "Bearclaw", 	value: 21}
];

let w = 800;
let h = 450;
let margin = {
	top: 20,
	bottom: 20,
	left: 20,
	right: 20
};

var width = w - margin.left - margin.right;
var height = h - margin.top - margin.bottom;

let x = d3.scale.linear()
		.domain([0, d3.max(data, (d) => {
    		return d.value;
    })])
		.range([0, width]);
var y = d3.scale.ordinal() 			// need distinct values eg keys
		.domain(data.map((entry) => {
			return entry.key;
		}))
		.rangeBands([0, height]); 	// used for distinct values

let svg = d3.select('body').append('svg')
						.attr('width', 800)
            .attr('height', 420)
            .attr('id', 'chart');
let chart = svg.append('g')
				.classed('display', true)
        .attr('transform', 'translate(20, 20)');

function plot(params) {
	// creating the bars
	// vertical bar graph
	this.selectAll('.bar')
		.data(params.data)
		.enter() 				// enter phase
		.append('rect')
		.attr('class', 'bar') 	// for future selections
		.attr('x', 0)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('width', (d, i) => {
			return x(d.value);		// x() does the scaling
		})
		.attr('height', (d, i) => {
			return y.rangeBand() - 1;
		});

	this.selectAll('.bar-label')
		.data(params.data)
		.enter()
		.append('text')
		.classed('bar-label', true)
		.attr('x', (d, i) => {
			return x(d.value);			// use css to change the anchor
		})
		.attr('dx', -4)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('dy', (d, i) => {
			return y.rangeBand()/1.5+2;
		})
		.text((d, i) => {
			return d.value;
		});
}

plot.call(chart, {
	data: data
});

Setting colour with colour scales

var data = [
	{key: "Glazed",		value: 132},
	{key: "Jelly",		value: 71},
	{key: "Holes",		value: 337},
	{key: "Sprinkles",	value: 93},
	{key: "Crumb",		value: 78},
	{key: "Chocolate",	value: 43},
	{key: "Coconut", 	value: 20},
	{key: "Cream",		value: 16},
	{key: "Cruller", 	value: 30},
	{key: "Éclair", 	value: 8},
	{key: "Fritter", 	value: 17},
	{key: "Bearclaw", 	value: 21}
];

let w = 800;
let h = 450;
let margin = {
	top: 20,
	bottom: 20,
	left: 20,
	right: 20
};

var width = w - margin.left - margin.right;
var height = h - margin.top - margin.bottom;

let x = d3.scale.linear()
		.domain([0, d3.max(data, (d) => {
    		return d.value;
    })])
		.range([0, width]);
var y = d3.scale.ordinal() 			// need distinct values eg keys
		.domain(data.map((entry) => {
			return entry.key;
		}))
		.rangeBands([0, height]); 	// used for distinct values

// alter colours using linear scale
let linearColorScale = d3.scale.linear()
						.domain([0, data.length])
						.range(['#572500', '#F68026']);

// ordinal for distinct colours
let ordinalColorScale = d3.scale.category20();

let svg = d3.select('body').append('svg')
						.attr('width', 800)
            .attr('height', 420)
            .attr('id', 'chart');
let chart = svg.append('g')
				.classed('display', true)
        .attr('transform', 'translate(20, 20)');

function plot(params) {
	// creating the bars
	// vertical bar graph
	this.selectAll('.bar')
		.data(params.data)
		.enter() 				// enter phase
		.append('rect')
		.attr('class', 'bar') 	// for future selections
		.attr('x', 0)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('width', (d, i) => {
			return x(d.value);		// x() does the scaling
		})
		.attr('height', (d, i) => {
			return y.rangeBand() - 1;
		})
		.style('fill', (d, i) => {
			return linearColorScale(i);
		});

	this.selectAll('.bar-label')
		.data(params.data)
		.enter()
		.append('text')
		.classed('bar-label', true)
		.attr('x', (d, i) => {
			return x(d.value);			// use css to change the anchor
		})
		.attr('dx', -4)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('dy', (d, i) => {
			return y.rangeBand()/1.5+2;
		})
		.text((d, i) => {
			return d.value;
		});
}

plot.call(chart, {
	data: data
});

Adding X and Y axis

// after the colour scales

let xAxis = d3.svg.axis() 			// svg portion of the d3 library
				.scale(x)
				.orient('bottom');

let yAxis = d3.svg.axis()
				.scale(y)
				.orient('left');

...

function plot(params) {
	// creating the bars
	// vertical bar graph
	this.selectAll('.bar')
		.data(params.data)
		.enter() 				// enter phase
		.append('rect')
		.attr('class', 'bar') 	// for future selections
		.attr('x', 0)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('width', (d, i) => {
			return x(d.value);		// x() does the scaling
		})
		.attr('height', (d, i) => {
			return y.rangeBand() - 1;
		})
		.style('fill', (d, i) => {
			return linearColorScale(i);
		});

	this.selectAll('.bar-label')
		.data(params.data)
		.enter()
		.append('text')
		.classed('bar-label', true)
		.attr('x', (d, i) => {
			return x(d.value);			// use css to change the anchor
		})
		.attr('dx', -4)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('dy', (d, i) => {
			return y.rangeBand()/1.5+2;
		})
		.text((d, i) => {
			return d.value;
		});
	this.append('g')
			.classed('x axis', true)
			.attr('transform', 'translate(' + 0  + ', ' + height  + ')')
			.call(xAxis);
	this.append('g')
			.classed('y axis', true)
			.attr('transform', 'translate(0, 0)')
			.call(yAxis);
}

Flipping the axes

How to create a column chart?

  • height needs to take an offset
  • other values essentially invert
  • text anchor will be middle in css
var data = [
	{key: "Glazed",		value: 132},
	{key: "Jelly",		value: 71},
	{key: "Holes",		value: 337},
	{key: "Sprinkles",	value: 93},
	{key: "Crumb",		value: 78},
	{key: "Chocolate",	value: 43},
	{key: "Coconut", 	value: 20},
	{key: "Cream",		value: 16},
	{key: "Cruller", 	value: 30},
	{key: "Éclair", 	value: 8},
	{key: "Fritter", 	value: 17},
	{key: "Bearclaw", 	value: 21}
];

let w = 800;
let h = 450;
let margin = {
	top: 20,
	bottom: 20,
	left: 20,
	right: 20
};

var width = w - margin.left - margin.right;
var height = h - margin.top - margin.bottom;

let x = d3.scale.ordinal() 			// need distinct values eg keys
		.domain(data.map((entry) => {
			return entry.key;
		}))
		.rangeBands([0, height]); 	// used for distinct values

let y = d3.scale.linear()
		.domain([0, d3.max(data, (d) => {
    		return d.value;
    	})])
    	.range([height, 0]);	// IMPORTANT CHANGE FROM [0, width]

// alter colours using linear scale
let linearColorScale = d3.scale.linear()
						.domain([0, data.length])
						.range(['#572500', '#F68026']);

// ordinal for distinct colours
let ordinalColorScale = d3.scale.category20();

let svg = d3.select('body').append('svg')
						.attr('width', 800)
            .attr('height', 420)
            .attr('id', 'chart');
let chart = svg.append('g')
				.classed('display', true)
        .attr('transform', 'translate(20, 20)');

function plot(params) {
	// creating the bars
	// vertical bar graph
	this.selectAll('.bar')
		.data(params.data)
		.enter() 				// enter phase
		.append('rect')
		.attr('class', 'bar') 	// for future selections
		.attr('x', (d, i) => {
			return x(d.key);
		})
		.attr('y', (d, i) => {
			return y(d.value);
		})
		.attr('width', (d, i) => {
			return x(d.value);		// x() does the scaling
		})
		.attr('height', (d, i) => {
			return x.rangeBand();
		})
		.style('fill', (d, i) => {
			return linearColorScale(i);
		});

	this.selectAll('.bar-label')
		.data(params.data)
		.enter()
		.append('text')
		.classed('bar-label', true)
		.attr('x', (d, i) => {
			return x(d.value);			// use css to change the anchor
		})
		.attr('dx', -4)
		.attr('y', (d, i) => {
			return y(d.key);
		})
		.attr('dy', (d, i) => {
			return y.rangeBand()/1.5+2;
		})
		.text((d, i) => {
			return d.value;
		});

		this.append('g')
			.classed('x axis', true)
			.attr('transform', 'translate(' + 0  + ', ' + height  + ')')
			.call(xAxis);
		this.append('g')
			.classed('y axis', true)
			.attr('transform', 'translate(0, 0)')
			.call(yAxis);
}

plot.call(chart, {
	data: data
});

Adding Gridlines

var yGridlines = d3.svg.axis() 				// create another "axis"
					.scale(y)
					.tickSize(-width, 0, 0) 			// used to adjust the axis
					.tickFormat('')
					.orient('left');

// add these grid lines with the call function at the start of the plot function

The grid lines also need to be styled! Hit up the CSS file to do this.

.gridline path,
.gridline line {
	fill: none;
	color: blue;
	shape-rendering: crispEdges;
}

Rotating the X axis titles

...
this.append('g')
			.classed('x axis', true)
			.attr('transform', 'translate(' + 0  + ', ' + height  + ')')
			.call(xAxis)
				.selectAll('text')
					.style('text-anchor', 'end')
					.attr('dx', -8)
					.attr('dy', 8)
					.attr('transform', 'translate(0,0), rotate(-45)');
this.append('g')
			.classed('y axis', true)
			.attr('transform', 'translate(0, 0)')
			.call(yAxis);
...

Adding axis labels

// within the plot function at the bottom

this.select('.y.axis')
	.append('text')
	.attr('x', 0)
	.attr('y', 0)
	.style('text-anchor', 'middle')
	.attr('transform', 'translate(-50, ' + height / 2 + ') rotate(-90)')
	.text('Units sold');

this.select('.x.axis')
	.append('text')
	.attr('x', 0)
	.attr('y', 0)
	.style('text-anchor', 'middle')
	.attr('transform', 'translate(' + width / 2 + ', 80) rotate(-90)')
	.text('Donut Type');

Updating the plot function with best practises

  • Add new parameter entries.
plot.call(chart, {
	data: data,
	axis: {
		x: xAxis,
		y: yAxis
	},
	gridlines: yGridlines
}
})

Secontion 5: Making the Chart Interactive

  • Sorting data using things like buttons.
  • Similary to jquery, with have d3 methods like "on"
  • Using the '+' prefix will convert the string to a number
  • To show updated data changes, we need to know about the phases // enter(), update(), exit()
  • we ensure this can happen by splitting the selectAll function where the updated phase is in the latter part - then in the exit phase we get rid of any elements that are no longer bound!
  • you must update the domains when you update data!
// do for all elements we wish to remove
this.selectAll('.bar')
	.data(params.data)
	.exit()
	.remove();