Piecewise linear quadratic (plq) function description
A plq function is a piecewise function, where each piece is either a linear or a quadratic polynomial. It is stored as the matrix, where each row represents one piece of the function.
Note that singleton indicator functions are given in a special form such that [x(1),0,0,c(1)] = I_{x(1)}(x) + c(1).
Bryan Gardiner
, University of British Columbia, BC, Canada