drawSharedFactor: Draw Shared Factor
In PatrickPfeifferDSc/bite: Bayesian Inference On Treatment Effects For Panel Data

Internal. draw_sharedfactor draws the latent factors f_i for SF model.

1 2	drawSharedFactor(epsx, lambdax, epsy, sgma2, lambda, start_x, nx, start_y, Tn, fix.f = FALSE)

`epsx`	residual vector on x
`lambdax`	lambda parameter of selection model x*
`epsy`	residuals on y
`sgma2`	variance parameters
`lambda`	lambda parameters on outcome for each panel time and treatment
`start_x`	indicator matrix
`nx`	number of observations
`start_y`	indicator matrix on y
`Tn`	number of observations times panel t