Item6696: ymin/ymax not having good defaults

Old way

Previously when ymin and ymax were not specified, the ChartPlugin would use the data's min/max as the starting point for ymin and ymax, but it would then pick a numygrids such that the Y increment between Y grid lines was a 1*, 2*, or 5*. ChartPlugin would then need to adjust the ymin and/or ymax to fit the new numygrids.

Unfortunately this resulted in odd ymin and ymax values that often were not human friendly

New way

The new way is to adjust ymin down to the nearest 1*, 2*, or 5* value and to adjust ymax up to the nearest 1*, 2*, or 5* value. numygrids is then found such that the Y grids has an increment that is as human friendly as possible

-- TWiki:Main/TaitCyrus - 2011-04-26

This change has been checked in and uploaded.

-- TaitCyrus - 2011-04-26