Introduce edge construction into the 'get.artifact.network.issue' function.
Connect 'add_link' and 'referenced_by' issue-events by an edge.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Add new 'add_link' and 'referenced_by' issue events to the testing data to
allow for new tests. Add a test for the construction of an issue-based
artifact-network with 'issues.only.comments' turned on and off.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

For some issue-events the 'event.info.1' column is to be interpreted as
a reference to an issue. In this case it is more consistent to reformat
the column entry into the <issue-[issue.source]-[event.info.1]> format.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

To be consistent with bipartite networks it is necessary to rename the
vertex attribute 'IssueEvent' to 'Issue' in multi-networks.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Modify 'split.data.time.based' to be able to split by activity-based bins.
Rename the function to 'split.data.by.time.or.bins'. Introduce wrapper
functions 'split.data.by.bins.vector' and 'split.data.time.based' to call
'split.data.by.time.or.bins'.

Add 'include.duplicate.ids' parameter in 'split.get.bins.activity.based'
to obtain bins covering all data elements from 'df' by which the split
is being performed, regardless of the elements ids uniqueness.

In 'split.data.activity.based', after calculating the bins to place data
elements into, replace the time-based splitting by
'split.data.by.bins.vector'. Time-based splitting is incorrect for the
case that the date of the last element in a bin is the same as the date
of the first element of the next bin.

Adjust calculation of 'offset.end' in 'split.data.activity.based' to fix
a bug where because of a short last window the end offset would cross
the border of the last window, overlapping into the second last. Because
of this overlap the last sliding windows would not be calculated as expected.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Instead of creating only undirected issue-based artifact-networks, we now
take the directedness information out of the network config. Edges are
already created in a way that they can be interpreted as directed
edges from the issue referencing to the referenced issue.

Replace for loop in edge creation by more efficient mclapply and fix
some minor formatting inconsistencies.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Rework the algorithm to create sliding windows in activity-based splitting.
Instead of cutting off half a range many elements at the end before building
sliding windows (which creates a lot of edge cases), build sliding windows with
every element up to the last one. Then remove the last incomplete range.
The contents of the last incomplete range will be fully included in the second
last range and therefore redundant.
Sometimes the last incomplete range is a regular range. Previously the last
range always had to be a regular range. This means that removing the last
incomplete range requires updating the tests.

Additionally fix and improve documentation of splitting methods and fix
minor spelling bugs.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

This renaming makes sense as the method only splits dataframes. Rename
'split.data.by.bins.vector' to 'split.data.by.bins' as it is more readable
and easier to understand.

This works towards se-sic#239.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Check type of the 'bins' parameter and its components in the wrapper
functions 'split.data.by.time' and 'split.data.by.bins'. Move
'split.data.by.time.or.bins' into a new category for internal helper
functions to discourage direct invocation.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Check if the 'bins' parameter of the 'split.data.by.bins' actually
contains 'bins' component. Use 'get.date.from.string' instead of
accessing 'lubridate::ymd_hms' directly, to encapsulate date conversion.
Allow 'vector' component of 'bins' to be of any subclass of
'numeric' instead of explicitly 'numeric'.

Disallow lists that contain elements that are not representing a date
in 'split.data.time.based' as they do not comply with the expected
format of bins for 'split.data.by.time.or.bins'.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Add tests that call 'split.data.time.based' and 'split.data.by.bins'
with various malformed 'bins' parameters and expect failure.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Reverse order of reference from Jira issue 332 and Jira issue 328, since
previously, Jira issue 332 was referenced before its creation.
Copy GitHub and Jira issue data from 'test_feature/feature' also to
'test_proximity/proximity' to keep the data consistent.

Adjust all effected tests to comply with the changed testing data.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland.de>

Also use backticks instead of single ticks for proper markdown highlighting.
Improve changelog messages by clarifing and properly focusing on the
important changes as well as adding more relevant commit hashes.

Signed-off-by: Maximilian Löffler <s8maloef@stud.uni-saarland>