**Next message:**Dmitry A. Shtol: "Re: [ROOT] Shared libraries."**Previous message:**Rene Brun: "Re: [ROOT] Shared libraries."**In reply to:**Rene Brun: "Re: [ROOT] Spline, tgraph and function fit"**Next in thread:**Rene Brun: "Re: [ROOT] Spline, tgraph and function fit"**Reply:**Rene Brun: "Re: [ROOT] Spline, tgraph and function fit"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Hi Rene, Thanks for the quick response and the addition. However, I was looking for something more. I guess I want a spline method that is simply a linear interpolation between points for which I can Eval. The TGraph::Eval method you created is a TSpline3 which does not simply interpolate between points. The problem is for regions in the data (x-axis is time) for which there is no data and the TSpline3 goes crazy between the two points (and a straight line between is approximately the correct answer). The application is tracking the stability of a value versus time where the value is approximately a constant (but with gaps in time with no reading). The current TGraph::Draw("L") method creates the lines but no TSpline is created which stores those lines. Does this make more sense? Or is there a way to make TSpline simply interpolate that I missed? Cheers, Kevin |------------------------------------|---------------------------------| | Kevin Reil | 2575 Sand Hill Road, MS 26 | | X2447, 103D A&E Bldg. 041 | Menlo Park, CA 94025 | |------------------------------------|---------------------------------| | http://www.slac.stanford.edu/~reil | Office (650) 926-2447 | | reil@slac.stanford.edu | Home (650) 938-1767 | | http://reil.no-ip.org | Fax (650) 926-5368 | |----------------------------------------------------------------------| | And my father dwelt in a tent. | |----------------------------------------------------------------------| On Wed, 17 Mar 2004, Rene Brun wrote: >Hi Kevin, > >I have added a new function in TGraph to make a spline interpolation between >points > >Double_t Eval(Double_t x, TSpline *spline=0) const; >// Interpolate points in this graph at x using a TSpline >// -if spline==0 a TSpline3 object is created using this graph >// and the interpolated value from the spline is returned. >// the internally created spline is deleted on return. >// -if spline is specified, it is used to return the interpolated value. > >Now in CVS > >Rene Brun > >Kevin Reil wrote: >> >> Hi all, >> >> I've attached below a dialogue I had before about TSpline::Eval. The >> method described has worked great. >> >> However, I want to get a pointer to a TSpline (simple spline not TSpline3 >> or TSpline5). >> >> If I have a graph (and assume it has some points filled x=0 to x=100) >> and if I draw the graph telling it to connect the dots "L" I get a simple >> spline. >> >> TGraph *gr; >> gr->Draw("L"); >> >> Is there in fact an object created so I could do something like. >> >> TGraph *gr; >> gr->Draw("L"); >> TSpline *s = (TSpline*)gROOT->FindObject("stemp"); >> // analagous to htemp from nt-Draw(); >> s->Eval(52.3); >> >> instead of >> >> TGraph *gr; >> gr->Draw("L"); >> TSpline3 *s = new TSpline3("grs",gr); >> s->Eval(52.3); >> >> Thanks, >> Kevin >> >> ----------------------------------------------------------------------------- >> >> Hi Kevin, >> >> You can use for example the TSpline class. Here is an example: >> You can use TSpline::Eval to evaluate the spline at a point x. >> >> { >> gROOT->Reset(); >> c1 = new TCanvas("c1","gerrors2",200,10,700,500); >> c1->SetFillColor(42); >> c1->SetGrid(); >> >> // draw a frame to define the range >> TH1F *hr = c1->DrawFrame(-0.4,0,1.2,12); >> hr->SetXTitle("X title"); >> hr->SetYTitle("Y title"); >> c1->GetFrame()->SetFillColor(21); >> c1->GetFrame()->SetBorderSize(12); >> >> // create first graph >> Int_t n1 = 9; >> Double_t x1[] = {-0.22, 0.05, 0.25, 0.35, 0.61,0.7,0.85,0.89,0.95}; >> Double_t y1[] = {1,2.9,5.6,7.4,9.6,8.7,6.3,4.5,2}; >> Double_t ex1[] = {.05,.1,.07,.07,.05,.06,.07,.08,.05}; >> Double_t ey1[] = {.8,.7,.6,.5,.4,.5,.6,.7,.8}; >> gr1 = new TGraphErrors(n1,x1,y1,ex1,ey1); >> gr1->SetMarkerColor(kBlue); >> gr1->SetMarkerStyle(21); >> gr1->Draw("LP"); >> >> // use a cubic spline to smooth the graph >> TSpline3 *s = new TSpline3("grs",gr1); >> s->SetLineColor(kRed); >> s->Draw("same"); >> } >> >> See also class TGraphSmooth >> >> Rene Brun >> >> Kevin Reil wrote: >> > >> > Hi, >> > >> > I was wondering if it is possible to Eval a spline fit. >> > >> > TGraph *gr = new TGraph(100,*x, *y); >> > gr->Draw("apl"); >> > >> > The l has made a nice spline fit from x=0 to x=100 for example. >> > >> > Now, I want to get the value from the spline line at say x=53.2 >> > Something like: >> > gr->FindObject("spline")->Eval(53.2); >> > >> > Thank you, >> > Kevin >> > >> > ------------------------------------------- >> > - Kevin Reil - >> > - #244A INSCC - >> > - http://www.physics.utah.edu/~reil - >> > - reil@physics.utah.edu - >> > ------------------------------------------- >> > - And my father dwelt in a tent. - >> > ------------------------------------------- >> >> |------------------------------------|---------------------------------| >> | Kevin Reil | 2575 Sand Hill Road, MS 26 | >> | X2447, 103D A&E Bldg. 041 | Menlo Park, CA 94025 | >> |------------------------------------|---------------------------------| >> | http://www.slac.stanford.edu/~reil | Office (650) 926-2447 | >> | reil@slac.stanford.edu | Home (650) 938-1767 | >> | http://reil.no-ip.org | Fax (650) 926-5368 | >> |----------------------------------------------------------------------| >> | And my father dwelt in a tent. | >> |----------------------------------------------------------------------| >> >> On Tue, 16 Mar 2004, Frank Winklmeier wrote: >> >> >Hi, >> > >> >I get the following error message on using TChain::GetEntry() >> > >> >root [28] chain.GetEntry(1,0) Error in <TBranch::GetBasket>: File: >> >BBbar-41.root at byte:0, branch:event, entry:-1 >> >(Int_t)(-1) >> > >> >Can somebody explain me what this error means and where it originally >> >comes from (it's not in TBranch::GetBasket)? How can I find out what's >> >wrong with this root file? >> > >> >Thanks, >> >Frank >> > >> > >> > > >

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