imclab/d3-transform

add an interface for svg transform attributes in d3.js

D3-Transform

d3-transform makes it easy to define and reuse functions that produce [transform][1] attribute strings for SVG elements. Using d3-transform reduces repetition, allows you to compose multiple transforms, and eliminates ugly string-interpolation from your d3 visualization code.

Installation

Include d3-transform in your web page using a script tag any time after you've included [d3][2]:

<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="/path/to/d3-transform.js"></script>

Usage

d3-transform replaces the manual construction of transform attribute strings for SVG elements. For example, if you want to translate, rotate, and scale a group element depending on the data bound to that element, you'd write something like this without d3-transform:

d3.select('svg').selectAll('g')
    .data([{ size: 5 }, { size: 10 }])
  .enter().append('g')
    .attr('transform', function(d, i) {
      return "translate(20," + d.size * 10 + ") rotate (40) scale(" + d.size + "2)");
    });

With d3-transform, you can rewrite the above code like this:

var transform = d3.svg.transform()
    .translate(function(d) { return [20, d.size * 10] })
    .rotate(40)
    .scale(function(d) { return d.size + 2 });

var svg = d3.select('svg.example1').selectAll('g')
    .data([{ size: 5 }, { size: 10 }])
    .enter()
    .append('g')
    .attr('transform', transform);

In both cases the resulting document will look the same:

<svg>
  <g transform="translate(20,50) rotate(40) scale(7)"></g>
  <g transform="translate(20,100) rotate(40) scale(12)"></g>
</svg>

You can specify arguments for these operations by either providing positional arguments to the corresponding method of the transform object, or by providing a function that will return an array of arguments that are interpreted as positional arguments. In the special case where an operation only takes one argument, your function can return a number.

All of the SVG 1.1 transform operations are supported: matrix, rotate, translate, scale, skewX, and skewY. See the [SVG 1.1 Specification][5] or [MDN][1] for further details on the arguments of each operation.

When using node.js, calls to require('d3-transform') return a direct reference to the "transform" method.

var d3 = require('d3');
var d3Transform = require('d3-transform');

var transform = d3Transform()
    .translate(function(d) { return [20, d.size * 10] })
    .rotate(40)
    .scale(function(d) { return d.size + 2 });

var svg = d3.select('svg.example1').selectAll('g')
    .data([{ size: 5 }, { size: 10 }])
    .enter()
    .append('g')
    .attr('transform', transform);

Composition

If you want to extend one transform with another set of operations, pass the initial transform object into the d3.svg.transform() function:

var transform1 = d3.svg.transform()
  .translate(10,20);

var transform2 = d3.svg.transform(transform1)
  .scale(function(d) { return [d.size];})

d3.select('svg.example2').selectAll('g')
    .data([{ size: 5 }, { size: 10 }])
  .enter().append('g')
    .attr('transform', transform2);

The result is a document that looks like this:

<svg>
  <g transform="translate(10,20) scale(5)"></g>
  <g transform="translate(10,20) scale(10)"></g>
</svg>

Contributors

• Erik Cunningham ([@trinary][3])
• Spiros Eliopoulos ([@seliopou][4])

License

MIT, see LICENSE.txt for details.

[1]: https://developer.mozilla.org/en-US/docs/SVG/Attribute/transform "Transform://developer.mozilla.org/en-US/docs/SVG/Attribute/transform "Transform" [2]: http://d3js.org [3]: https://twitter.com/trinary [4]: https://twitter.com/seliopou [5]: http://www.w3.org/TR/2011/REC-SVG11-20110816/coords.html#TransformAttribute