m = gjp (m, k[, l])

 m: matrix; k, l: row- and column-index of pivot, l defaults to k.

 Gauss-Jordon pivot as defined in Bard, Y.: Nonlinear Parameter
 Estimation, p. 296, Academic Press, New York and London 1974. In
 the pivot column, this seems not quite the same as the usual
 Gauss-Jordan(-Clasen) pivot. Bard gives Beaton, A. E., 'The use of
 special matrix operators in statistical calculus' Research Bulletin
 RB-64-51 (1964), Educational Testing Service, Princeton, New Jersey
 as a reference, but this article is not easily accessible. Another
 reference, whose definition of gjp differs from Bards by some
 signs, is Clarke, R. B., 'Algorithm AS 178: The Gauss-Jordan sweep
 operator with detection of collinearity', Journal of the Royal
 Statistical Society, Series C (Applied Statistics) (1982), 31(2),
 166--168.

Package: optim