当前位置: 首页>>代码示例>>C++>>正文


C++ TVectorD::Use方法代码示例

本文整理汇总了C++中TVectorD::Use方法的典型用法代码示例。如果您正苦于以下问题:C++ TVectorD::Use方法的具体用法?C++ TVectorD::Use怎么用?C++ TVectorD::Use使用的例子?那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在TVectorD的用法示例。


在下文中一共展示了TVectorD::Use方法的1个代码示例,这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞,您的评价将有助于系统推荐出更棒的C++代码示例。

示例1: solveLinear

void solveLinear(Double_t eps = 1.e-12)
{
   cout << "Perform the fit  y = c0 + c1 * x in four different ways" << endl;

   const Int_t nrVar  = 2;
   const Int_t nrPnts = 4;

   Double_t ax[] = {0.0,1.0,2.0,3.0};
   Double_t ay[] = {1.4,1.5,3.7,4.1};
   Double_t ae[] = {0.5,0.2,1.0,0.5};

   // Make the vectors 'Use" the data : they are not copied, the vector data
   // pointer is just set appropriately

   TVectorD x; x.Use(nrPnts,ax);
   TVectorD y; y.Use(nrPnts,ay);
   TVectorD e; e.Use(nrPnts,ae);

   TMatrixD A(nrPnts,nrVar);
   TMatrixDColumn(A,0) = 1.0;
   TMatrixDColumn(A,1) = x;

   cout << " - 1. solve through Normal Equations" << endl;

   const TVectorD c_norm = NormalEqn(A,y,e);

   cout << " - 2. solve through SVD" << endl;
   // numerically  preferred method

   // first bring the weights in place
   TMatrixD Aw = A;
   TVectorD yw = y;
   for (Int_t irow = 0; irow < A.GetNrows(); irow++) {
      TMatrixDRow(Aw,irow) *= 1/e(irow);
      yw(irow) /= e(irow);
   }

   TDecompSVD svd(Aw);
   Bool_t ok;
   const TVectorD c_svd = svd.Solve(yw,ok);

   cout << " - 3. solve with pseudo inverse" << endl;

   const TMatrixD pseudo1  = svd.Invert();
   TVectorD c_pseudo1 = yw;
   c_pseudo1 *= pseudo1;

   cout << " - 4. solve with pseudo inverse, calculated brute force" << endl;

   TMatrixDSym AtA(TMatrixDSym::kAtA,Aw);
   const TMatrixD pseudo2 = AtA.Invert() * Aw.T();
   TVectorD c_pseudo2 = yw;
   c_pseudo2 *= pseudo2;

   cout << " - 5. Minuit through TGraph" << endl;

   TGraphErrors *gr = new TGraphErrors(nrPnts,ax,ay,0,ae);
   TF1 *f1 = new TF1("f1","pol1",0,5);
   gr->Fit("f1","Q");
   TVectorD c_graph(nrVar);
   c_graph(0) = f1->GetParameter(0);
   c_graph(1) = f1->GetParameter(1);

   // Check that all 4 answers are identical within a certain
   // tolerance . The 1e-12 is somewhat arbitrary . It turns out that
   // the TGraph fit is different by a few times 1e-13.

   Bool_t same = kTRUE;
   same &= VerifyVectorIdentity(c_norm,c_svd,0,eps);
   same &= VerifyVectorIdentity(c_norm,c_pseudo1,0,eps);
   same &= VerifyVectorIdentity(c_norm,c_pseudo2,0,eps);
   same &= VerifyVectorIdentity(c_norm,c_graph,0,eps);
   if (same)
      cout << " All solutions are the same within tolerance of " << eps << endl;
   else
      cout << " Some solutions differ more than the allowed tolerance of " << eps << endl;
}
开发者ID:Y--,项目名称:root,代码行数:77,代码来源:solveLinear.C


注:本文中的TVectorD::Use方法示例由纯净天空整理自Github/MSDocs等开源代码及文档管理平台,相关代码片段筛选自各路编程大神贡献的开源项目,源码版权归原作者所有,传播和使用请参考对应项目的License;未经允许,请勿转载。