This extension adds a few helper methods that are useful for CKAN’s views. It uses the new Resource View developed in https://github.com/ckan/ckan/tree/1251-resource-view.
To use it, simply clone this repository and run python setup.py install.
Then add viewhelpers to your ckan.plugins in your CKAN config file.
Make sure you add it before the other plugins that depend on it.
Finally, restart your webserver. The helpers are now available for the other plugins.
When building a visualization, it’s often useful to allow the user to filter the data shown, so she can focus on what’s more important to her.
We defined a filtering scheme inspired on OpenSpending. First I’ll explain how it works, and then I’ll point you to examples where you can learn how to use it in your visualizations. Say that you have this dataset:
| Country | Forest area (% of land area) | Year |
|---|---|---|
| Brazil | 68.0 | 1990 |
| Brazil | 66.2 | 1995 |
| Brazil | 64.5 | 2000 |
| Brazil | 62.7 | 2005 |
| Brazil | 61.4 | 2010 |
| USA | 32.4 | 1990 |
| USA | 32.6 | 1995 |
| USA | 32.8 | 2000 |
| USA | 33.0 | 2005 |
| USA | 33.2 | 2010 |
| … | … | … |
Source: http://data.worldbank.org/indicator/AG.LND.FRST.ZS/countries
This is just a snippet of the dataset. It has data for every country, from 1980 until 2013. Plotting all this data in a single chart (say a line chart) wouldn’t be very useful. You have to filter.
Our filtering works by adding a filters parameter to the URL’s query string.
For example, if you wanted to see the data just from Brazil, you’d do:
?filters=Country:Brazil
To keep it short, I’m just showing the query string, but keep in mind that there’s the whole > URL before that (i.e.
http://demo.ckan.org/dataset/world-bank/resource/b395830e-8848-4e18-84b2-43dsaf4359)
What if I wanted both Brazil and USA (but nothing else)?
?filters=Country:Brazil|Country:USA
What if I wanted Brazil and USA, but only on 1990 and 2010?
?filters=Country:Brazil|Country:USA|Year:1990|Year:2010
In general, the filters are defined as Key:Value pairs separated by |
(pipes). If you have multiple filters on the same key, it works as a logical
OR (i.e. Country == "Brazil" OR Country == "USA"). If you have multiple
filters defined on different keys, it works as a logical AND (i.e. Country
== "Brazil" AND Year == "1990").
To see how this is used in real extensions, check ckanext-dashboard, ckanext-basiccharts, and ckanext-mapviews.
If you have any doubts, the code itself should be relatively easy to follow. The JavaScript tests might help as well.
When creating your visualization as a CKAN’s resource view, you might want to allow the user to define default forms. For example, she might want to create multiple bar charts on the same resource, each showing a part of the data.
To help you create the form allowing the user to do that, we’ve created the
filters_form CKAN module. Currently it’s still under heavy development, and
the Jinja macros used to make it look like the screenshot above weren’t moved
to this repository yet (there’s an issue for that at
#4).
You can see how it was done in ckanext-basiccharts. If you want (or does) use it on your resource view, please ping me in the aforementioned issue.
Copyright (C) 2014 Open Knowledge Foundation
This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License along with this program. If not, see http://www.gnu.org/licenses/.
CKAN Extensions