How to supply matrix data to a TMatrixDSparse object?

ROOT
1

___i want to supply data to a TMatrixDSparse object with 6 rows and 5 columns, the TMatrixDSparse object i want is:

image
image1893×661 45.2 KB

here is the code:

TMatrixDSparse matrixs(6,5);
Int_t rowindex[]{0,0,1,3,3,3,4,5,5};
Int_t colindex[]{0,2,1,2,3,4,2,3,4};
const Double_t data[]{3,4,2,8,3,5,5,6,3};
matrixs.SetRowIndexArray(rowindex);
matrixs.SetColIndexArray(colindex);
matrixs.SetMatrixArray(data);

it seems i fail to assign data.

something is wrong with the code?
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ROOT Version: 6.24/02
Platform: Ubuntu 20.04
_Compiler:_GCC 9.3.0

2

Hi,

This is the correct code. You should use the right signature of SetMatrixArray for the sparse matrix. See Mathematical libraries - ROOT

{
   TMatrixDSparse matrixs(6,5);
   Int_t rowindex[]{0,0,1,3,3,3,4,5,5};
   Int_t colindex[]{0,2,1,2,3,4,2,3,4}; 
   Double_t data[]{3,4,2,8,3,5,5,6,3};                                                                           
   matrixs.SetMatrixArray(9,rowindex,colindex,data);

   matrixs.Print();
}
3

It seems TMatrixDSparse class has no construtor function like this:
SetMatrixArray(9,rowindex,colindex,data)

4

It is not a constructor but a member function, see
https://root.cern.ch/doc/master/classTMatrixTSparse.html#a273d8dce890bbdcd83b2b5c5c1b2392a