JarCastingD3-Transform
d3-transform makes it easy to define and reuse functions that produce transform 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:
<script src="http://d3js.org/d3.v4.min.js"></script>
<script src="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.transform()
.translate(function(d) { return [20, d.size * 10] })
.rotate(40)
.scale(function(d) { return d.size + 2 });
var svg = d3.select('svg').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 or MDN 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.transform() function:
var transform1 = d3.transform()
.translate(10,20);
var transform2 = d3.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);
Another way to compose multiple transform objects is to use the seq operation:
var transform1 = d3.transform()
.translate(10,20);
var transform2 = d3.transform()
.scale(function(d) { return [d.size];})
var transform =
transform1.seq(transform2);
With either of these approaches, 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
- Spiros Eliopoulos @seliopou
- Micah Stubbs @micahstubbs