Managing multiple focal levels in Table Lens

The Table Lens, focus+context visualization for large data tables, allows users to see 100 times as many data values as a spreadsheet in the same screen space in a manner that enables an extremely immediate form of exploratory data analysis. In the original Table Lens design, data are shown in the context area using graphical representations in a single pixel row. Scaling up the Table Lens technique beyond approximately 500 cases (rows) by 40 variables (columns) requires not showing every value individually and thus raises challenges for preserving the exploratory and navigational ease and power of the original design. We describe two design enhancements for introducing regions of less than a pixel row for each data value and discuss the issues raised by each.