Class for mapping variables in residuals vs predictions/time plot
See also
Other DataMapping classes: 
BoxWhiskerDataMapping,
CumulativeTimeProfileDataMapping,
DDIRatioDataMapping,
GroupMapping,
Grouping,
HistogramDataMapping,
ObsVsPredDataMapping,
ObservedDataMapping,
PKRatioDataMapping,
PieChartDataMapping,
QQDataMapping,
RangeDataMapping,
ResVsTimeDataMapping,
TimeProfileDataMapping,
TornadoDataMapping,
XYDataMapping,
XYGDataMapping
Super classes
tlf::XYDataMapping -> tlf::XYGDataMapping -> tlf::ObsVsPredDataMapping -> ResVsPredDataMapping