save_faust_pop: Save FAUST subset as an FCS file
In MiguelRodo/faustutils: Additional functions to extract and plot FAUST output

Save a specified FAUST-identified population to project_path/faustData/fcsData as an FCS file for all samples gated or just a specified subset.

save_faust_pop(
  project_path,
  pop,
  fr_source = NULL,
  sample = NULL,
  trans_fn = NULL,
  trans_chnl = NULL
)

`project_path`	character. FAUST project directory.
`pop`	`list` or `named character vector`. If a `character vector`, then all cells matching the set of marker levels are returned. If a `list`, then each element must be a `character vector`, and then all cells matching either of these specified sets of marker levels are returned.
`fr_source`	GatingSet or character vector. If a `GatingSet`, then the flowFrames within the GatingSet are used to create the output fcs files. If a character vector, then must specify a directory containing FCS files. These FCS files are used to create the output fcs files.
`sample`	integer vector or character vector. If an integer vector, then it specifies the indices of the samples for which to save output. If character, then it specifies the names of the sames to save output for. If `NULL`, then the output for every sample is saved. Default is `NULL`.
`trans_fn`	function. If supplied, this function is applied to the expression data. Useful for back-transformation. If `NULL`, then no transformation is applied. Default is `NULL`.
`trans_chnl`	character vector. If specified, `trans_fn` is applied to only these channels. If `NULL` and if `trans_fn` is not `NULL`, then `trans_fn` is applied to entire expression matrix. Default is `NULL`.