file: The .cov covariance Nonmem matrix file to read
auto.ext: If TRUE (default) the extension will automatically be modified using NMdataConf()$file.cov. This means file can be the path to an input or output control stream, and NMreadCov() will still read the .cov file.
...: Passed to fread
Returns
A matrix with covariance step from NONMEM
Details
This function is taken from nonmem2rx::nmcov which was based on NMdata::NMreadTab.