freeCodeCamp/curriculum/challenges/chinese/04-data-visualization/data-visualization-with-d3/add-attributes-to-the-circle-elements.md

---
id: 587d7fab367417b2b2512bd8
title: Add Attributes to the Circle Elements
challengeType: 6
forumTopicId: 301471
dashedName: add-attributes-to-the-circle-elements
---

# --description--

The last challenge created the `circle` elements for each point in the `dataset`, and appended them to the SVG canvas. But D3 needs more information about the position and size of each `circle` to display them correctly.

A `circle` in SVG has three main attributes. The `cx` and `cy` attributes are the coordinates. They tell D3 where to position the *center* of the shape on the SVG canvas. The radius (`r` attribute) gives the size of the `circle`.

Just like the `rect` `y` coordinate, the `cy` attribute for a `circle` is measured from the top of the SVG canvas, not from the bottom.

All three attributes can use a callback function to set their values dynamically. Remember that all methods chained after `data(dataset)` run once per item in `dataset`. The `d` parameter in the callback function refers to the current item in `dataset`, which is an array for each point. You use bracket notation, like `d[0]`, to access the values in that array.

# --instructions--

Add `cx`, `cy`, and `r` attributes to the `circle` elements. The `cx` value should be the first number in the array for each item in `dataset`. The `cy` value should be based off the second number in the array, but make sure to show the chart right-side-up and not inverted. The `r` value should be 5 for all circles.

# --hints--

Your code should have 10 `circle` elements.

```js
assert($('circle').length == 10);
```

The first `circle` element should have a `cx` value of 34, a `cy` value of 422, and an `r` value of 5.

```js
assert(
  $('circle').eq(0).attr('cx') == '34' &&
    $('circle').eq(0).attr('cy') == '422' &&
    $('circle').eq(0).attr('r') == '5'
);
```

The second `circle` element should have a `cx` value of 109, a `cy` value of 220, and an `r` value of 5.

```js
assert(
  $('circle').eq(1).attr('cx') == '109' &&
    $('circle').eq(1).attr('cy') == '220' &&
    $('circle').eq(1).attr('r') == '5'
);
```

The third `circle` element should have a `cx` value of 310, a `cy` value of 380, and an `r` value of 5.

```js
assert(
  $('circle').eq(2).attr('cx') == '310' &&
    $('circle').eq(2).attr('cy') == '380' &&
    $('circle').eq(2).attr('r') == '5'
);
```

The fourth `circle` element should have a `cx` value of 79, a `cy` value of 89, and an `r` value of 5.

```js
assert(
  $('circle').eq(3).attr('cx') == '79' &&
    $('circle').eq(3).attr('cy') == '89' &&
    $('circle').eq(3).attr('r') == '5'
);
```

The fifth `circle` element should have a `cx` value of 420, a `cy` value of 280, and an `r` value of 5.

```js
assert(
  $('circle').eq(4).attr('cx') == '420' &&
    $('circle').eq(4).attr('cy') == '280' &&
    $('circle').eq(4).attr('r') == '5'
);
```

The sixth `circle` element should have a `cx` value of 233, a `cy` value of 355, and an `r` value of 5.

```js
assert(
  $('circle').eq(5).attr('cx') == '233' &&
    $('circle').eq(5).attr('cy') == '355' &&
    $('circle').eq(5).attr('r') == '5'
);
```

The seventh `circle` element should have a `cx` value of 333, a `cy` value of 404, and an `r` value of 5.

```js
assert(
  $('circle').eq(6).attr('cx') == '333' &&
    $('circle').eq(6).attr('cy') == '404' &&
    $('circle').eq(6).attr('r') == '5'
);
```

The eighth `circle` element should have a `cx` value of 222, a `cy` value of 167, and an `r` value of 5.

```js
assert(
  $('circle').eq(7).attr('cx') == '222' &&
    $('circle').eq(7).attr('cy') == '167' &&
    $('circle').eq(7).attr('r') == '5'
);
```

The ninth `circle` element should have a `cx` value of 78, a `cy` value of 180, and an `r` value of 5.

```js
assert(
  $('circle').eq(8).attr('cx') == '78' &&
    $('circle').eq(8).attr('cy') == '180' &&
    $('circle').eq(8).attr('r') == '5'
);
```

The tenth `circle` element should have a `cx` value of 21, a `cy` value of 377, and an `r` value of 5.

```js
assert(
  $('circle').eq(9).attr('cx') == '21' &&
    $('circle').eq(9).attr('cy') == '377' &&
    $('circle').eq(9).attr('r') == '5'
);
```

# --seed--

## --seed-contents--

```html
<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 svg = d3.select("body")
                  .append("svg")
                  .attr("width", w)
                  .attr("height", h);

    svg.selectAll("circle")
       .data(dataset)
       .enter()
       .append("circle")
       // Add your code below this line



       // Add your code above this line

  </script>
</body>
```

# --solutions--

```html
<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 svg = d3.select("body")
                  .append("svg")
                  .attr("width", w)
                  .attr("height", h);

    svg.selectAll("circle")
       .data(dataset)
       .enter()
       .append("circle")
       .attr("cx", (d) => d[0])
       .attr("cy", (d) => h - d[1])
       .attr("r", 5)

  </script>
</body>
```