Roman Mackovcak has been doing some performance testing. In his blog he addresses the problems he encountered while trying to visualize all of the data he collected.
traditional spreadsheets are good to show sales for four regions, but they have problems with hundreds or thousands of data samples.
Roman's solution was to use GNUPlot to create his charts for him. In his opinion, the advantages of using GNUPlot over a traditional spreadsheet is the ability to automate the process. However these advantages to come with a cost. GNUPlot must be scripted using Ruby. Roman offers his scripts for download. He also explains how his scripts work with a couple of screen shots. He cautions that the scripts are very simple and will not work for all data files. He is interested in feedback including bug reports from anyone who may decide to use it.