Generate null data
generate_null.RdThis function doesn't allow of much flexbility, and is meant primarily for simple null simulations. Here, `n` (the number of cells) is equal to `cell_per_person*num_individuals`.
Value
a list with covariates (a `matrix` with `n` cells and
4 columns, named `"Intercept"`, `"Log_UMI"`, `"Sex"`, and `"Age"`,
which will be used in `eSVD2::initialize_esvd`),
df (a `data.frame` with `num_individuals` rows
and 5 columns, named named `"Intercept"`, `"Log_UMI"`, `"Sex"`, `"Age"`, and `"Individual"`),
metadata_individual (a `matrix` with `n` rows and 1 column called `"Individual"` for
which cell originates from which individual)
nat_mat (a `n` by `p` `matrix` denoting the natural parameter for each cell's gene expression), and
obs_mat (a `n` by `p` `dgCMatrix` denoting the observed count for each cell's gene expression),