spawning_matrix: arrange the rxy values and IDs into a matrix for spawning...
In eriqande/CohoBroodstock:

This will write out the matrix to two files, as well. One for Libby and the other for the hatchery (in which the Rxy values are not given)

1 2	spawning_matrix(Rxy_tidy = NULL, Rxy_path = NULL, rxy_cutoff = 0.1, file_prefix = "")

`Rxy_tidy`	a long-format (tidy, three columns) spawning matrix like you would get out of compute Rxy. Must be given if Rxy_path is not.
`Rxy_path`	the path to the Rxy matrix. Must be given if Rxy_tidy is not.
`rxy_cutoff`	Any male with an Rxy value greater than this to a certain female will have two asterices attached to its name so that the hatchery knows not to spawn him with this female. Defaults to 0.1.
`file_prefix`	Files will come out named file_prefix + spawn_matrix_full.csv and file_prefix + spawn_matrix.csv. By default this is blank. You can use this to specify a path to use as well. By default it comes out in the current working directory.