class TUnfoldSys: public TUnfold

 set all pointers to zero

 arguments:
    hist_A:  matrix that describes the migrations
    histmap: mapping of the histogram axes to the unfolding output
    regmode: global regularisation mode
 data members initialized to something different from zero:
    fDA2, fDAcol

 add a correlated error source
    sysError: alternative matrix or matrix of absolute/relative shifts
    name: name of the error source
    histmap: mapping of the histogram axes to the unfolding output
    mode: format of the error source

 initialize pointers and TMaps

 delete all data members

 clear all data members which depend on the unfolding results

 calculations required for syst.error
 data members modified
    fVYAx, fESparse, fEAtV, fAE, fAEAtV_one,
    fErrorUncorrX, fErrorUncorrAx, fErrorCorrX, fErrorCorrAx

 get output error contribution from statistical fluctuations in A
   ematrix: output error matrix histogram
   binMap: see method GetEmatrix()
   clearEmat: set kTRUE to clear the histogram prior to adding the errors
 data members modified:
   fVYAx, fESparse, fEAtV, fErrorAStat

 prepare matrix of uncorrelated systematic errors
   m1,m2 : coefficients for propagating the errors
 the result depends on the errors
   fDA2, fDA2col

 prepare error matrix of correlated systematic shifts
   m1,m2 : coefficients for propagating the errors
   dsys : matrix of correlated shifts from this source

 calculate systematic error matrix from a given source
    ematrix: output
    source: name of the error source
    binMap: see method GetEmatrix()
    clearEmat: set kTRUE to clear the histogram prior to adding the errors

 calculate total systematic error matrix
    ematrix: output
    binMap: see method GetEmatrix()
    clearEmat: set kTRUE to clear the histogram prior to adding the errors

 get total error including statistical error
    ematrix: output
    binMap: see method GetEmatrix()

 calculate total chi**2 including systematic errors