a square numeric or complex matrix containing the coefficients of
the linear system. Logical matrices are coerced to numeric.
a numeric or complex vector or matrix giving the right-hand
side(s) of the linear system. If missing, b is taken to be
an identity matrix and solve will return the inverse of a.
the tolerance for detecting linear dependencies in the
columns of a. The default is .Machine$double.eps. Not
currently used with complex matrices a.
logical. Defunct and ignored.
further arguments passed to or from other methods
a or b can be complex, but this uses double complex
arithmetic which might not be available on all platforms.
The row and column names of the result are taken from the column names
of a and of b respectively. If b is missing the
column names of the result are the row names of a. No check is
made that the column names of a and the row names of b
For back-compatibility a can be a (real) QR decomposition,
although qr.solve should be called in that case.
qr.solve can handle non-square systems.
Unsuccessful results from the underlying LAPACK code will result in an
error giving a positive error code: these can only be interpreted by
detailed study of the FORTRAN code.