what does ppval means...????

While calculating the curvature a command ppval is used. What does it mean and what it does here...??

s=spline(x,y) s1=s; s1.order=s.order-1; s2=s1; s2.order=s1.order-1;

A1=ppval(s1,x); A2=ppval(s2,x);

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/matlab/ref/ppval.html

Evaluate piecewise polynomial