A Timeline will present a series of values to be used for an axis. Each Timeline must provide transformation methods between domain values and timeline values.
A timeline can be used as parameter to a {@link org.jfree.chart.axis.DateAxis} to define the values that this axissupports. This class implements a timeline formed by segments of equal length (ex. days, hours, minutes) where some segments can be included in the timeline and others excluded. Therefore timelines like "working days" or "working hours" can be created where non-working days or non-working hours respectively can be removed from the timeline, and therefore from the axis. This creates a smooth plot with equal separation between all included segments.
Because Timelines were created mainly for Date related axis, values are represented as longs instead of doubles. In this case, the domain value is just the number of milliseconds since January 1, 1970, 00:00:00 GMT as defined by the getTime() method of {@link java.util.Date}.
In this class, a segment is defined as a unit of time of fixed length. Examples of segments are: days, hours, minutes, etc. The size of a segment is defined as the number of milliseconds in the segment. Some useful segment sizes are defined as constants in this class: DAY_SEGMENT_SIZE, HOUR_SEGMENT_SIZE, FIFTEEN_MINUTE_SEGMENT_SIZE and MINUTE_SEGMENT_SIZE.
Segments are group together to form a Segment Group. Each Segment Group will contain a number of Segments included and a number of Segments excluded. This Segment Group structure will repeat for the whole timeline.
For example, a working days SegmentedTimeline would be formed by a group of 7 daily segments, where there are 5 included (Monday through Friday) and 2 excluded (Saturday and Sunday) segments.
Following is a diagram that explains the major attributes that define a segment. Each box is one segment and must be of fixed length (ms, second, hour, day, etc).
start time | v 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ... +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+... | | | | | |EE|EE| | | | | |EE|EE| | | | | |EE|EE| +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+... \____________/ \___/ \_/ \/ | | included excluded segment segments segments size \_________ _______/ \/ segment groupLegend:
In the example, the following segment attributes are presented:
Exception Segments are allowed. These exception segments are defined as segments that would have been in the included segments of the Segment Group, but should be excluded for special reasons. In the previous working days SegmentedTimeline example, holidays would be considered exceptions.
Additionally the startTime, or start of the first Segment of the smallest segment group needs to be defined. This startTime could be relative to January 1, 1970, 00:00:00 GMT or any other date. This creates a point of reference to start counting Segment Groups. For example, for the working days SegmentedTimeline, the startTime could be 00:00:00 GMT of the first Monday after January 1, 1970. In this class, the constant FIRST_MONDAY_AFTER_1900 refers to a reference point of the first Monday of the last century.
A SegmentedTimeline can include a baseTimeline. This combination of timelines allows the creation of more complex timelines. For example, in order to implement a SegmentedTimeline for an intraday stock trading application, where the trading period is defined as 9:00 AM through 4:00 PM Monday through Friday, two SegmentedTimelines are used. The first one (the baseTimeline) would be a working day SegmentedTimeline (daily timeline Monday through Friday). On top of this baseTimeline, a second one is defined that maps the 9:00 AM to 4:00 PM period. Because the baseTimeline defines a timeline of Monday through Friday, the resulting (combined) timeline will expose the period 9:00 AM through 4:00 PM only on Monday through Friday, and will remove all other intermediate intervals.
Two factory methods newMondayThroughFridayTimeline() and newFifteenMinuteTimeline() are provided as examples to create special SegmentedTimelines. @see org.jfree.chart.axis.DateAxis
| |