This function performs the reparameterization step originally described in Carter, G. W., Hays, M., Sherman, A. & Galitski, T. Use of pleiotropy to model genetic interactions in a population. PLoS Genet. 8, e1003010 (2012).
calc_m(markers, beta_m)
This function returns a matrix with one row holding the m12 and m21 values as described in Carter et al. 2012
A vector of length two holding the names of the markers being tested.
The matrix of beta values from the pairwise linear regression testing the interaction between the markers.