wormtrails

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Wormtrails

The general idea is this:

• a CHART object contains a bunch of BUCKETs and knows about a bunch of THINGs

• a BUCKET holds a number of SAMPLEs. A bucket might represent a weekend (for box offices), an hour (for measuring samples across a 24 hour period), a day, etc. A bucket is identified within a chart by a numerical index. For example, the box office buckets are identified by indexes of the form 200801, meaning the first weekend of 2008. Hourly buckets are indexed from 0 to 23. BUCKETs with the same index are EQ.

• a THING represents a discrete item being tracked over time. For the IRC charts, that's a nickname. For the movie charts, that's a movie. The THING's name is used as a unique identifier; all THINGs with the same name are EQ.

• a SAMPLE is the aggregate value of a THING in a BUCKET. The value might represent a simple count, as in the IRC and referer charts, or the monetary gross, as in the movie charts. Before layout, a SAMPLE is

The CHART is the top-level data structure. The steps are generally:

• create a CHART (or subclass) object

• use ADD-DATA for a simple way to create and accumulate BUCKET, THING, and SAMPLE objects into the CHART

• lay out the CHART with LAYOUT; this establishes the rectangles associated with SAMPLEs and their relative positions on an abstract canvas

Drawing with vecto:

• draw the labels and grid for the entire CHART

• draw the rectangles for each SAMPLE into the PNG and add connecting glue

  • the colors for each samplebox/glue are taken from the color of the THING. the colors of each thing are initialized with ESTABLISH-COLORS. See RAINBOW-COLOR-MIXIN in wormtrails.lisp to see an example of how to set colors up by the position of the debut bucket for a thing, or irc.lisp to see how to set colors of a thing based on which bucket the max sample value falls in.

• draw the labels for each THING with DRAW-LABEL. The default method does that by drawing the CHART-LABEL of the THING into the SCREENBOX of an appropriate SAMPLE for the THING, as found with BEST-LABEL-SAMPLE

  • the default method for BEST-LABEL-SAMPLE just returns first sample that would fit the label, but it can be specialized. The IRC example changes things to use the sample with the maximum value

  • (samples thing) returns a list of all samples for a THING, and could be used for some other criteria to select one to draw

• draw the labels for each BUCKET with DRAW-LABEL; the default method just draws the CHART-LABEL of the BUCKET beneath the bounding box of the bucket

  • CHART-LABEL for a BUCKET could be specialized to produce a prettier string than just the numerical index; for example the IRC hours are converted to HH:00, with MIDNIGHT and NOON returned for 0 and 12 respectively

Scaling is important to get a chart that looks pretty. I haven't determined any automatic way to do scaling yet; I just fiddle with values. Using consistent scaling also makes it much easier to compare chart-to-chart.

The imagemap in this version is somehwat primitive. You will need to change the link and onmouseover actions in WRITE-IMAGEMAP-AREA to do something useful if you want to use the PNG/imagemap capability.

I think irc.lisp, referers.lisp, and pastes.lisp are good ways to figure out how to get started with simple stuff. More complex stuff, just let me know.