transfer_solve_subproblem: Solve subproblems via coordinate descent, given the parameter...
In pengminshi/cFIT: cFIT (common Factor Space Integration & Transfer)

Solve the subproblem given which parameter set to update. For each subproblem, the exact solution is obtained

transfer_solve_subproblem(
  params.to.update = c("lambda", "b", "H"),
  X,
  W,
  H,
  b,
  lambd,
  verbose = T
)

`params.to.update`	a characteristic scalar, choice of (lambda','b','H'), specifying which set of parameters to update
`X`	An ncells-by-ngenes gene expression matrix
`W`	An ngenes-by-r reference low dimensional factor matrix
`H`	A factor loading matrix of size ncells-by-r
`b`	A numeric shift vector of size p (ngenes).
`lambd`	A numeric scaling vector of size p (ngenes)
`verbose`	boolean scalar, whether to show extensive program logs (default TRUE)