Purpose

Duplicated Lines (%) shows a percentage of duplicated lines in the project code compared to a total amount of lines of code (LOC) on the project.

How metric helps

The worst consequence of a big number of duplicates is a case when a software vulnerability is copied, the vulnerability may continue to exist in the copied code if the developer is not aware of such copies. Refactoring of duplicated code can improve many software metrics, such as lines of code, complexity. This may lead to shorter compilation times, lower cognitive load, less human error, and fewer forgotten or overlooked pieces of code.

How metric works

Chart Overview

Duplicate code lines values are shown in % (Axis Y) and distributed over time (Axis X) on the chart.

Calculation 

Duplicated Lines (%) = Duplicated Lines / LOC * 100%,

where

Duplicated Lines - a number of duplicates

LOC - number of all code lines

RAG thresholds: Green <= 2%, Amber <=10%, Red >10%.

Data Source

Data for the metric can be collected from Sonar.