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ckanext-basiccharts

This extension adds Line, Bar and Pie charts to CKAN, using the new Resource View that are still being developed on the master branch (currently unreleased).

It uses Flot Charts, which is compatible with all major browsers (including IE6+).

Installation

Clone this repository and run python setup.py install. Then add which charts you'd like to your ckan.plugins in your CKAN config file.

You can then enable any (or all) of:

  • linechart
  • barchart
  • piechart
  • basicgrid

Finally, restart your webserver. You should see the new chart types as options in the view type's list on any resource that's in the DataStore.

Usage

There are 3 kind of attributes that define what the chart will be: filters, axes, and groups. We'll create charts in the next sections to define them all using the following data:

State Date Population
California 01-01-1990 29,760,021
California 01-01-2000 33,871,648
California 01-01-2010 37,253,956
New York 01-01-1990 17,990,455
New York 01-01-2000 18,976,457
New York 01-01-2010 19,378,102

Filters

If you don't want all data to be plotted in the chart, you can add filters. Here, you define what to include.

For example, with the sample data, if you want to display just for California, you'd create the filter:

State: California

Multiple filters on the same column work as OR. For example, to plot just the data for 01-01-2000 and 01-01-2010, you'd do:

Date: 01-01-2000
Date: 01-01-2010

Multiple filters on different columns work as AND. If we'd add all filters defined in the last paragraphs, we would plot data only for California in 01-01-2000 or 01-01-2010. In techie terms, it'll be State == "California" AND (Date == "01-01-2000" OR Date == "01-01-2010")

Currently you can't exclude data, only include. There's no way to negate a filter (to all states that are not California, for example).

To learn more about filters, check ckanext-viewhelpers.

Axes

This defines what column will be plotted in each axis. Line and bar charts have two axes, Y and X; pie charts only have one, Y.

As long as the DataStore interpreted the column types correctly, the charts will work with any kind of data (numeric, text, or date). To check if this is the case, check the Upload log in the Manage resource's DataStore tab. You should see something like:

Determined headers and types: [{'type': u'text', 'id': u'State'}, {'type':
u'timestamp', 'id': u'Date'}, {'type': u'numeric', 'id': u'Population'}]

Just confirm that the types defined are correct. If not, try to understand why and fix it, as the charts created might behave incorrectly. The DataStore's documentation might help you.

Groups

This allows you to group the data being plotted, based on a certain column. It's optional for bar and line charts, but required for pie charts.

For example, say that you want to create a line chart that shows California and New York's population growth. You define Date to be your X axis, and Population to be your Y axis. Then, when you preview the chart, it'll be like:

Timeline of population growth without groups

Not what you'd want. The problem is that when there's no group, all data is groupped together. You'd like to separate the population from California from the New York's. To do that, you need to group by State.

Timeline of population growth groupped by state

Much better. Notice that there's a group's legend as well. To enable it, you need to check Show groups' legend.

The bar chart works similarly. The pie charts are a bit different. To define them, you're required to set up a column to group by. With the same data, if you'd want to create a chart for, given the sum of California and New York's population, which percentage belongs to one and which to the other, you'd set up group by as State, and Y axis as Population. That'll create:

Timeline of population growth groupped by state

Beware that as we have multiple rows for the same group, what's being plotted on the pie chart is the sum of all values. In this case, the sum of the population in 1990, 2000, and 2010. If you want a single year, add a filter.

As the legends are always embedded in the chart, there's no Show groups' legend option.

Common problems

There are no side-by-side bars

If you'd tried plotting a timeline of the population growth in California and New York as a bar chart, as we did in the last section using a line chart, you'd end up with something like this:

Timeline of population growth groupped by state as bars

Don't let this fool you. It looks like a stacked bar chart, but it's not (there's no stacked bars chart as well). The bars aren't stacked, they're drawn over each other. This almost always isn't what you want. To fix it, we need to support side-by-side bars, but we don't yet. If you'd like to help, check issue #8.

License

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/.

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Line, bar and pie charts for CKAN

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