bi scaling of rows and columns

[stephens999]

we should think about possibility of dealing with biscaling (eg as in softImpute)

[NKweiwang]

can we just call their function?

[stephens999]

yes, but I think we should think about how the output should be. For example, we might
have flash(Y,biscale=TRUE) output L and F that correspond to the original Y (even thought they were computed first by biscaling). My hope is that we might be able to compare objective functions
based on a "biscale model" vs nonscaled model to decide if biscaling is a good idea.