This feature is important to web marketers and to a web analytics solution in general. The user should be able to select two periods to compare in the Piwik UI. The graphs, tables, sparklines, texts, would show values for both periods as well as the % of evolution.
Attachment: compare periods nice ui.png
Related to comparing segments https://github.com/piwik/piwik/issues/7716 since both would use same mechanism
Depends on #397: graph to plot multiple lines
nobody is working on it.
The best way if you would like to contribute this back to core, is to post here your specification of what you want to do and how you are planning to do it, and we might be able to review and help you out. This is not a trivial task so it requires careful planning. that would be great new feature though
Adding mockups as attachments.
(In ) Refs #5711
idSubtable, in period compare mode, is now of format $ID_CURRENT_DATE-$ID_COMPARED_DATE the ViewDataTable then parses this idSubtable to load both data tables correctly.
It now works fine on simple datatable, I need to also port this to action data table (page views)
(In ) Refs #5711 remove duplicated <td>
Development has stopped in the branch. Moving this to post 1.0
This feature might be picked up soon as requests are increasing. If you are interested in sponsoring the feature, please contact us at services at piwik.org
Note that the code in the branch cannot be reused, but definitely a good place to look at for ideas on how to implement this the easiest way.
Comparing 2 reports together is useful for dates, but also to compare visitor segments (eg. All visitors VS Visitors coming from Adwords) - see #2135
See this example to integrate "Time comparisons" in a table: http://www.shufflepoint.com/assets/slides/267_prr.png
But a green/red indicator might be as good or better than 2 horizontal lines per row...
This would be used - In all tables in the UI when comparing 2 periods - In the PDF/Email reports by default (compared to N-1 period)
Work is being done in #3013 to add support for plotting multiple data values on a Static graph.
This feature would allow to implement "Compare to last period" feature in Email reports (Pdf/HTML), as a first "easier" step to implementing this feature.
We could implement the comparisons in the graphs (#3013) and add green/red percentages for every row of other report tables.