# How to transform a Monte Carlo PDF set into a Hessian PDF set

A Monte Carlo PDF set can be transformed into a Hessian PDF using the method described in [CFKR16] a runcard like the one below. In this example Neig are the number of basis eigenvectors of the Hessian PDF and mc2hname is an optional argument that can be added to give a custom name to the Hessian PDF set, if mc2hname is not defined, a default name will automatically be given to the Hessian PDF set. By default installgrids is False, by setting it to True we make sure that the Hessian PDF is added to the LHAPDF folder.

pdf: NNPDF31_nlo_as_0118

Neig: 100 # Number of basis eigenvectors of the Hessian PDF set
Q: 10 # Energy scale at which the MC PDF set is sampled
mc2hname: MyHessianPDF # Name of the Hessian PDF set
installgrid: True

actions_:
- mc2hessian