Improved infrastructure for creating graphs.

[eike-welk]

Implement improvements for infrastructure for generating graphs. The infrastructure should depend as few libraries as possible.

• Filters for selecting prices or listings. (Currently diagrams can only be made for prices.)
• Several algorithms for creating graphs:
  • histogram for month or week, rotated 90°, half transparent in background.
  • compute average (or median) from some type of values (eg. "observed")
  • compute standard deviation.
  • manipulations of time axis, for repeating time axis
  • number of sold items per month as separate diagram.
  • implement TODOs in code.
• clicking on price symbol goes to price or listing.

Matplotlib FAQ: http://matplotlib.org/1.2.1/faq/usage_faq.html

Different examples of Matplotlib usage compared: http://sjohannes.wordpress.com/2010/06/11/using-matplotlib-in-a-web-application/

Embedding python into QT: http://karmela.fsb.hr/site/files/1363350567-0-matplotlibforpythondevelopers2009.pdf

Done:

• Basic infrastructure, useful for GUI and report generator.
  • sold items bold, not sold items light
  • estimated items small, observed and guessed items big.