% put some stuff somewhere
\NDPput[x=1.2, y=75, RefPoint=br]{text}
\NDPput[x=1.2, y=100, Rot=45]{$a^2+b^2$}
% or put nodes...
\NDPput[x=1.6, y=100]{\pnode{A}}
\NDPput[x=1.8, y=150]{\pnode{B}}
% ...and draw a line between them
\ncline{A}{B}
% .. with text
\naput{$e^2$}
% or put the legend at a specific position
\NDPput[x=1.8, y=75]{\LegendDefinition{
\LegLine{style=StdLineStyA} & IdentI
}}
\end{NumericDataPlot}