Storing TMatrixD in a root file

Hi!

Iam trying to store TMatrixD objects efficiently in a ROOT file. I first of all tried to just add them to the root file. But because for a TMatrixD object one can not set a “name” this seems not to work. Then I tried a TMap together with a TObjString, but also without success. Finally I tried to use a TTree, where every matrix is stored as a TBranch. But here the filling of the matrices seemed not to work. An additional problem is that i try to do it with Python. Can anybody tell me what the best solution is? So far it looks like this:

# prepare ROOT and open the file
    from ROOT import TFile, TTree, TString, TObjString, TMatrixD, TPair
    from array import array
    theFile = TFile(rootfile, "recreate")

    theMatrix = TMatrixD(x,y)

        # fill the matrices
        for matrix in parser.MyMatrices:
            for row in range(0,matrix.nrows):
                for column in range(0,matrix.ncolumns):
                    theMatrix[row][column] = float(matrix.data[row][column])
            theMatrix.Write()
        theFile.Write()

    # write and close
    theFile.Close()

Here the version with tree and branches:

# prepare ROOT and open the file
 from ROOT import TFile, TTree, TString, TObjString, TMatrixD
 from array import array
 theFile = TFile(rootfile, "recreate")
    

 #make tree name ROOT save
 treename = filename.replace("-","_").split(".")[0]
 theTree = TTree(treename, "DataTree")

        # create all needed branches
        branchBuffers = []
        branchname_base = "Matrix"
        theMatrix = TMatrixD(x,y)

        for timestep in range(0, len(parser.MyMatrices)):

            branchBuffers.append(theMatrix)
            branchname = branchname_base+"_%s" %timestep
            print branchname
            tmp = theTree.Branch(branchname, "TMatrixD", branchBuffers[timestep])

        # fill the matrices
        for branchBuffer, matrix in zip(branchBuffers, parser.MyMatrices):
            for row in range(0, matrix.nrows):
                for column in range(0, matrix.ncolumns):
                   theMatrix[row][column] = float(matrix.data[row][column])
                   print theMatrix[row][column]
                   branchBuffer[0][0] = theMatrix[row][column]
            theTree.Fill()
        theFile.Write()

    # write and close
    theFile.Close()

The [0][0] looks strange but worked in the one dimensional case for vectors…
The interesting is, the two branches are in the root file, but when I load both branches the content (the correct values of the matrix) is the same, the right values only appear when I switch between GetEntry(0) and GetEntry(1)…But there only should be one entry in each branch… ?

Cheers,
Stefan

For the non-tree case, you simply use:

For the tree case, you need to make to call theTree.Fill() only once (aka move it one indentation level down)

Cheers,
Philippe

Hi!

Thanks a lot. Yes, this was one major problem. I have still to get used to the python style :wink:
One more thing had to be changed in the case of trees:

#make tree name ROOT save
        treename = filename.replace("-","_").split(".")[0]
        theTree = TTree(treename, "DataTree")

        # create all needed branches and buffers
        branchBuffers = []
        branchname_base = "Matrix"

        for timestep in range(0, len(parser.MyMatrices)):

            branchBuffers.append(TMatrixD(parser.MyMatrices[0].nrows, parser.MyMatrices[0].ncolumns))
            branchname = branchname_base+"_%s" %timestep
            print branchname
            tmp = theTree.Branch(branchname, "TMatrixD", branchBuffers[timestep])

        # fill the matrices
        for index, matrix in zip(xrange(10000), parser.MyMatrices):
            print "--------------------------"
            for row in range(0, matrix.nrows):
                print "row: "
                print row
                for column in range(0, matrix.ncolumns):
                   print float(matrix.data[row][column])
                   branchBuffers[index][row][column] = float(matrix.data[row][column])
        theTree.Fill()
        theFile.Write()

The “theMatrix” was removed and the content filled directly. Now it works. Just as information for people who might also need a similar solution…

Thanks a lot for the quick answers!
ROOT rulez… 8)