ListSweeps: List Sweeps
In patrickreidy/ag501: Carstens AG501 Electromagnetic Articulograph

List the .pos and .txt files for sweeps. Vectorized over path and pattern arguments.

1 2	ListSweeps(path = ".", pattern = "*", fullNames = TRUE, simplify = TRUE, recursive = FALSE, dropMissing = TRUE)

`path`	A character vector of paths to directories that contain sweeps (pairs of `.pos` and `.txt` files that share the same basename). Tilde expansion (see `path.expand`) is performed. Default value corresponds to the present working directory.
`pattern`	An optional vector of `regular expressions`. The length of this vector should be equal to the length of the `path` argument, or equal to `1`, in which case the same regular expression is used to match sweeps in each directory listed in `path`. Only sweeps whose basenames match the regular expression(s) will be returned. Default value matches all available sweeps. Patterns are always case-sensitive.
`fullNames`	If `TRUE`, then the full paths for the `.pos` and `.txt` files are returned. If `FALSE`, then the basenames for these files are returned. Default is `TRUE`.
`simplify`	If `TRUE`, then the table of sweeps found for each element in `path` are row-binded together into a single data table. If `FALSE`, then the tables of sweeps found for the elements in `path` are returned as elements of a list.
`recursive`	If `TRUE`, then the search recurses into subdirectories of elements of `param`. If `FALSE`, then the search only looks immediately in the directories listed in `path`.
`dropMissing`	If `TRUE`, then sweeps that are missing either a `.pos` or a `.txt` file are not listed. If `FALSE`, then sweeps with a missing file are listed.