From 40e5a5811c6ffce9b0974e93cdd927cbcf60c157 Mon Sep 17 00:00:00 2001 From: Joe Hunkeler Date: Tue, 11 Aug 2015 16:51:37 -0400 Subject: Repatch (from linux) of OSX IRAF --- math/slalib/doc/invf.hlp | 66 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 math/slalib/doc/invf.hlp (limited to 'math/slalib/doc/invf.hlp') diff --git a/math/slalib/doc/invf.hlp b/math/slalib/doc/invf.hlp new file mode 100644 index 00000000..e1d8588e --- /dev/null +++ b/math/slalib/doc/invf.hlp @@ -0,0 +1,66 @@ +.help invf Jun99 "Slalib Package" +.nf + + SUBROUTINE slINVF (FWDS,BKWDS,J) + + - - - - - + I N V F + - - - - - + + Invert a linear model of the type produced by the + slFTXY routine. + + Given: + FWDS d(6) model coefficients + + Returned: + BKWDS d(6) inverse model + J i status: 0 = OK, -1 = no inverse + + The models relate two sets of [X,Y] coordinates as follows. + Naming the elements of FWDS: + + FWDS(1) = A + FWDS(2) = B + FWDS(3) = C + FWDS(4) = D + FWDS(5) = E + FWDS(6) = F + + where two sets of coordinates [X1,Y1] and [X2,Y1] are related + thus: + + X2 = A + B*X1 + C*Y1 + Y2 = D + E*X1 + F*Y1 + + the present routine generates a new set of coefficients: + + BKWDS(1) = P + BKWDS(2) = Q + BKWDS(3) = R + BKWDS(4) = S + BKWDS(5) = T + BKWDS(6) = U + + such that: + + X1 = P + Q*X2 + R*Y2 + Y1 = S + T*X2 + U*Y2 + + Two successive calls to slINVF will thus deliver a set + of coefficients equal to the starting values. + + To comply with the ANSI Fortran standard, FWDS and BKWDS must + not be the same array, even though the routine is coded to + work on the VAX and most other computers even if this rule + is violated. + + See also slFTXY, slPXY, slXYXY, slDCMF + + P.T.Wallace Starlink 11 April 1990 + + Copyright (C) 1995 Rutherford Appleton Laboratory + Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. + +.fi +.endhelp -- cgit