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When looking at the code quality of an application and willing trying to decide on a plan of an action plan, it is sometimes not sufficient always enough to get a snapshot of the quality at a given time. You also need some visibility on into the application history to take the right decision.

For example, let's say that you have defined a requirement that each application should have a coverage by unit tests of 60%. And let's say that one of you your application has got 50% coverage. Without historical data, you can only conclude that the team does not write sufficient unit tests and that it should become the next focus of attention. But let's now say that a couple of months ago the coverage for this application was 20%... then you would probably conclude that although the requirement is not made yet, the team is doing a very good job and that no special focus needs to be put on unit tests. This is why having access to historical information is important.

Sonar provides this historical information through two features: Historical information is provided through the Time Machine and the Tendencies


The Time Machine is made of two generic widgets that can be instantiated and configured in added to any dashboard.

Timeline Widget

The Timeline widget provides the capability ability to display a chart containing historical data of up to 3 metrics. Passing your mouse over the timeline will display the different values.


titleThe Timeline is not displayed at package level by default

By default, historical information is not kept on directories/packages and therefore the timeline has not value no values to display below the project or module level. This can be changed by logging in as an a System administrator, going to Configuration Settings > General Settings > General > Database Cleaner and setting the Clean history data of directories/packages property to truefalse. This Note that this will increase the volume of data to be stored in the database.


This widget can be customized: 

History Table Widget

The History Table widget provides the capability to display a table with the historical data for up to 10 metrics:

This widget can be customized: 

Default Dashboard

titleAvailabe since Sonar 3.0.


A default Time  Time Machine dashboard comes out-of-the-box when installing Sonar. This is a combination of Timeline and History Table widgets:


What are Tendencies?

The tendencies are arrows that are displayed next to metrics in the dashboards. Those arrows show the trend for the measure.

How to Read Tendencies?

Sonar uses 5 levels to describe the tendency of a measure. Each level is represented by an arrow:


There are five different levels of tendency

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Strong increase

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Medium increase



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Medium decrease

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Strong decrease

Sonar uses black ( Image Removed) arrows Black arrows are used to represent tendencies on the quantitative metrics (the ones that are does not reflecting reflect quality of the code, for example number of lines of code). 
Sonar uses red ( Image Removed)
Red or green Image Removed) arrows are used to represent tendencies on the qualitative metrics (the ones that are reflecting reflects quality of the code, for example code coverage). The red Red is used when the quality decreases, the green when it increases. Of course, it is to be noted that if the percentage of duplicated lines decreases it will be represented in green by Image Removed because it is considered as an improvement.

How are Tendencies Calculated?

To compute the tendencies, making using a simple difference between the last two measures of each metric would not be accurate enough. Therefore Sonar implements a more advanced algorithm is implementedthe least squares method. The least squares It is a linear regression analysis that helps removing remove the noise in order to determine a trend on discrete measures. In other words, Sonar takes all the measure taken in the last XX days , checks that are taken into account, then the set of measures is checked to see if it makes some sense (by testing the correlation rate), determines and an estimated slope is computed and displays it displayed using the arrows. 


It is to be noted that the algorithm currently considers that measures are taken at a constant frequency

It is possible to configure the tendencies by logging in as an a System administrator and going to Configuration Settings > General Settings > General > Differential Views.


 To configure the number of days used to compute tendencies, set


the Tendency period property to the desired number of days. Default is 30.

Managing History

Whatever the reason (wrong quality profile, issue with analysis, etc.), it is possible to remove a snapshot to polish the Time Machine widgets. Note that the last snapshot can never be deleted.

For every snapshot, it is possible to manually:

  • Add, rename or remove a version
  • Add, rename or remove an event

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House Cleaning

Removing Useless Data

When you do a new analysis of your project, some data that were present in Sonar will not be accessible anymore. For example the source code of the previous analysis, measures at file level... These data will automatically be removed at the end of a new analysis.

Removing Un-necessary Analysis

This is very useful to analyze frequently a project in Sonar to see progress on quality. It is also very useful to be able to see the trends over weeks / months / years. But when you are back in time, you do not really need the same level of details as you would for one week ago. The Database Cleaner aims to delete some rows in database to save some space and to improve overall performances. Here is its default configuration:

  • it deletes all data older than 5 years
  • it keeps a single monthly analysis by project over 1 year
  • it keeps a single weekly analysis by project over 1 month
  • analysis with an event are kept

These settings can be changed in the page Settings > Configuration > General Settings > Database Cleaner.

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See also