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)
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.
This function returns a matrix with one row holding the m12 and m21 values as described in Carter et al. 2012