Cedar

Cedar is a library for crafting, sharing and data visualizations powered by ArcGIS Services. Built with D3 and the Vega graphics grammar, Cedar extends them with bindings for making templated chart graphics that can be re-used with different datasets.

At the highest level, Cedar provides a simple chart API. Beyond that it is possible to create new and unique chart types that can be loaded and customized through interactions and styling depending on your needs.

Currently Esri Cedar is in development and should be thought of as a beta or preview.

Types of Charts

While Cedar provides a set of commonly used chart types including Bar, Line, Scatterplot, and Pie through use of the Vega grammar it is possible for developers to create unique and custom charts that can be used by other developers with new data sources.

When starting with Cedar, we suggest that you begin by exploring the simple charts using your own data services. As you experiment with the interactions with Maps and more complex interaction you can also customize these charts with new capabilities such as legends, size scaling or labeling. Finally, you can fork and create completely custom chart templates that you then provide for other developers to use through Cedar.

Getting Started

Loading Cedar

You can load Cedar and its dependencies by including script tags. This will make the Cedar global availabe to your application.

<script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script type="text/javascript" src="http://vega.github.io/vega/vega.min.js"></script>
<script type="text/javascript" src="https://rawgit.com/Esri/cedar/master/src/cedar.js"></script>
<script>
  var chart = new Cedar({"type": "bar"});
  ...
</script>

Altenatively, you can use Dojo loader that is bundled with the ArcGIS API for JavaScript, to load Cedar and its dependencies by declaring them as packages:

<link rel="stylesheet" href="http://js.arcgis.com/3.13/esri/css/esri.css">
<script>
  window.dojoConfig = {
    async: true,
    packages: [
      {
        name: 'd3',
        location: 'http://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5',
        main: 'd3.min'
      }, {
        name: 'topojson',
        location: 'http://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19',
        main: 'topojson.min'
      }, {
        name: 'vega',
        location: 'http://vega.github.io/vega/',
        main: 'vega.min'
      }, {
        name: 'cedar',
        location: window.location.pathname.substring(0, window.location.pathname.lastIndexOf('/')) + '/../js',
        main: 'cedar'
      }
    ]
  };
</script>
<script src="http://js.arcgis.com/3.13/"></script>
<script>
  require('cedar', function(Cedar) {
    var chart = new Cedar({"type": "bar"});
    ...
  });
</script>

Using Cedar

Once Cedar is loaded you can create and show the chart at a designated element as follows:

  //create a cedar chart using the known 'bar' type
  // this is the same as passing {"specification": "path/to/cedar/charts/bar.json"}
  var chart = new Cedar({"type": "bar"});

  //create the dataset w/ mappings
  var dataset = {
    "url":"http://maps2.dcgis.dc.gov/dcgis/rest/services/DCGIS_DATA/Education_WebMercator/MapServer/5",
    "query": {
      "groupByFieldsForStatistics": "ZIP_CODE",
      "outStatistics": [{
        "statisticType": "sum", 
        "onStatisticField": "TOTAL_STUD", 
        "outStatisticFieldName": "TOTAL_STUD_SUM"
      }]
    },
    "mappings":{
      "sort": "TOTAL_STUD_SUM DESC",
      "x": {"field":"ZIP_CODE","label":"ZIP Code"},
      "y": {"field":"TOTAL_STUD_SUM","label":"Total Students"}
    }
  };

  //assign to the chart
  chart.dataset = dataset;

  //show the chart
  chart.show({
    elementId: "#chart"
  });

See the API documentation and examples for further details.

Demos

Here is are an extensive set of demos showing the concepts of Cedar.

Components of a Cedar Chart

Cedar charts are defined by the following ingredients:

• a Specification is a JSON document which includes,
• inputs that declare the variables of the chart such as category or value to be summarized
• template is a declarative syntax for chart design using the Vega visualization grammar.
• a dataset
• either url link to the ArcGIS Feature Layer;
• ...or values can be an array of inline features
• mappings bind the Feature Layer attributes to the Specification inputs
• and overrides are specific modifications to the Specification template

See the API documentation for further details.

Development Instructions

Make sure you have the Grunt CLI installed.

1. cd into the cedar folder
2. Install the dependencies with npm install
3. Install additional dependencies with bower install (if you encounter an error connecting to github take a look at this thread for a possible fix).
4. Run grunt docs from the command line. This will start the web server locally at http://localhost:8081 and start watching the source files and running linting and testing commands.
5. Push your changes using grunt docs:deploy which pushes to your origin/gh-pages
6. Create a pull request to esri/cedar/master

Dependencies

• D3 version 3 or higher is required but the latest version is recommended.
• Vega

Versioning

For transparency into the release cycle and in striving to maintain backward compatibility, Cedar is maintained under the Semantic Versioning guidelines and will adhere to these rules whenever possible.

Releases will be numbered with the following format:

<major>.<minor>.<patch>

And constructed with the following guidelines:

• Breaking backward compatibility bumps the major while resetting minor and patch
• New additions without breaking backward compatibility bumps the minor while resetting the patch
• Bug fixes and misc changes bumps only the patch

For more information on SemVer, please visit http://semver.org/.

Licensing

Copyright 2015 Esri

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

A copy of the license is available in the repository's LICENSE file.

[](Esri Tags: Visualization) [](Esri Language: JavaScript)