[pstricks] arrows on a curve

[Cyrille Piatecki]

Dear all,

I would like to know how to putsome arrow on a curve plot with psplot

Secondly in pst-solides3d.doc p133 it is explained how to define a  
function with  \defFunction before to use \psProjection. Could it be  
possible to use the procedure not with a function bu with a data file ?

Thanks

Cyrille Piatecki