The package bspline, downloadable from Statistical Software Components, now has three commands. The first, bspline, generates a basis of Schoenberg B-splines. The second, frencurv, generates a basis of reference splines whose parameters in the regression model are simply values of the spline at...

Economic theory often provides us with qualitative information on the properties of the functions in a model but rarely indicates their explicit functional form. Among these properties one can find monotonicity, concavity and supermodularity, which involve restricting the sign of the...