derivative of cubic spline

*To*: mathgroup at smc.vnet.net*Subject*: [mg66543] derivative of cubic spline*From*: "Jaccard Florian" <Florian.Jaccard at he-arc.ch>*Date*: Fri, 19 May 2006 03:40:20 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Dear All, I would like to know how to derivate a spline function constructed by Mathematica. The question has already been posted in : [mg25221] First derivative of interpolated spline But I wasn't able to find an answer in mathgroup. Example : data={{0, 1}, {1, 2.3}, {2, 2.5}, {3, 1.2}, {4, 0.47}, {5, 0.38}, {6, 0.76}} << "Numericalmath`SplineFit`" s = SplineFit[data, Cubic]; You can see that the spline is good : ParametricPlot[s[x], {x, 0, 6}, PlotStyle -> Blue, Epilog -> {{Blue, Text[HoldForm[y = s(x)], {2.5, g1[2.5]}, Background -> White]}, ({PointSize[0.03], Red, Point[#1]} & ) /@ data}, PlotRange -> {-0.5, 3}, TextStyle -> {FontFamily -> Times}]; But D[s[t],t] or s'[t] or so one doesn't help... So I'm not able to see that the spline is better than Interpolation (in the sense of a continuous derivative)! Please help! It's the first time I found something that is easier in MathCad than in Mathematica... Regards F.Jaccard florian.jaccard at he-arc.ch