Invert a linear model of the type produced by the slaFitxy routine.
fwds double[6] model coefficients
bkwds double[6] inverse model *j int status: 0 = OK, -1 = no inverse The models relate two sets of [x,y] coordinates as follows.
fwds[0] = a fwds[1] = b fwds[2] = c fwds[3] = d fwds[4] = e fwds[5] = f Where two sets of coordinates [x1,y1] and [x2,y1] are related
x2 = a + b*x1 + c*y1 y2 = d + e*x1 + f*y1
bkwds[0] = p bkwds[1] = q bkwds[2] = r bkwds[3] = s bkwds[4] = t bkwds[5] = u
x1 = p + q*x2 + r*y2 y1 = s + t*x2 + u*y2 Two successive calls to slaInvf will thus deliver a set of coefficients equal to the starting values. See also slaFitxy, slaPxy, slaXy2xy, slaDcmpf P.T.Wallace Starlink 30 October 1993