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587d7fad367417b2b2512bdf

Add Axes to a Visualization

src
https://cdnjs.cloudflare.com/ajax/libs/d3/4.3.0/d3.min.js

Description

Another way to improve the scatter plot is to add an x-axis and a y-axis. D3 has two methods axisLeft() and axisBottom() to render the y and x axes, respectively. (Axes is the plural form of axis). Here's an example to create the x-axis based on the xScale in the previous challenges: const xAxis = d3.axisBottom(xScale); The next step is to render the axis on the SVG canvas. To do so, you can use a general SVG component, the g element. The g stands for group. Unlike rect, circle, and text, an axis is just a straight line when it's rendered. Because it is a simple shape, using g works. The last step is to apply a transform attribute to position the axis on the SVG canvas in the right place. Otherwise, the line would render along the border of SVG canvas and wouldn't be visible. SVG supports different types of transforms, but positioning an axis needs translate. When it's applied to the g element, it moves the whole group over and down by the given amounts. Here's an example:

const xAxis = d3.axisBottom(xScale);

svg.append("g")
.attr("transform", "translate(0, " + (h - padding) + ")")
.call(xAxis);

The above code places the x-axis at the bottom of the SVG canvas. Then it's passed as an argument to the call() method. The y-axis works is the same way, except the translate argument is in the form (x, 0). Because translate is a string in the attr() method above, you can use concatenation to include variable values for its arguments.

Instructions

The scatter plot now has an x-axis. Create a y-axis in a variable named yAxis using the axisLeft() method. Then render the axis using a g element. Make sure to use a transform attribute to translate the axis by the amount of padding units right, and 0 units down. Remember to call() the axis.

Tests

tests:
  - text: Your code should use the <code>axisLeft()</code> method with <code>yScale</code> passed as the argument.
    testString: 'assert(code.match(/\.axisLeft\(yScale\)/g), ''Your code should use the <code>axisLeft()</code> method with <code>yScale</code> passed as the argument.'');'
  - text: 'The y-axis <code>g</code> element should have a <code>transform</code> attribute to translate the axis by (60, 0).'
    testString: 'assert($(''g'').eq(1).attr(''transform'').match(/translate\(60\s*?,\s*?0\)/g), ''The y-axis <code>g</code> element should have a <code>transform</code> attribute to translate the axis by (60, 0).'');'
  - text: Your code should call the <code>yAxis</code>.
    testString: 'assert(code.match(/\.call\(yAxis\)/g), ''Your code should call the <code>yAxis</code>.'');'

Challenge Seed

<body>
  <script>
    const dataset = [
                  [ 34,     78 ],
                  [ 109,   280 ],
                  [ 310,   120 ],
                  [ 79,   411 ],
                  [ 420,   220 ],
                  [ 233,   145 ],
                  [ 333,   96 ],
                  [ 222,    333 ],
                  [ 78,    320 ],
                  [ 21,   123 ]
                ];
    
    const w = 500;
    const h = 500;
    const padding = 60;
    
    const xScale = d3.scaleLinear()
                     .domain([0, d3.max(dataset, (d) => d[0])])
                     .range([padding, w - padding]);
    
    const yScale = d3.scaleLinear()
                     .domain([0, d3.max(dataset, (d) => d[1])])
                     .range([h - padding, padding]);
    
    const svg = d3.select("body")
                  .append("svg")
                  .attr("width", w)
                  .attr("height", h);
    
    svg.selectAll("circle")
       .data(dataset)
       .enter()
       .append("circle")
       .attr("cx", (d) => xScale(d[0]))
       .attr("cy",(d) => yScale(d[1]))
       .attr("r", (d) => 5);
    
    svg.selectAll("text")
       .data(dataset)
       .enter()
       .append("text")
       .text((d) =>  (d[0] + "," + d[1]))
       .attr("x", (d) => xScale(d[0] + 10))
       .attr("y", (d) => yScale(d[1]))
    
    const xAxis = d3.axisBottom(xScale);
    // Add your code below this line
    const yAxis = undefined;
    // Add your code above this line
    
    svg.append("g")
       .attr("transform", "translate(0," + (h - padding) + ")")
       .call(xAxis);
    
    // Add your code below this line
    
    
    
    // Add your code above this line
  
  </script>
</body>

Solution

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