From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 4 Mar 2015 21:21:30 -0500 Subject: Initial commit --- src/slalib/sun67.htx/node123.html | 122 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) create mode 100644 src/slalib/sun67.htx/node123.html (limited to 'src/slalib/sun67.htx/node123.html') diff --git a/src/slalib/sun67.htx/node123.html b/src/slalib/sun67.htx/node123.html new file mode 100644 index 0000000..a3d1a77 --- /dev/null +++ b/src/slalib/sun67.htx/node123.html @@ -0,0 +1,122 @@ + + + + +SLA_INVF - Invert Linear Model + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_KBJ - Select Epoch Prefix +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_INTIN - Decode an Integer Number +

+

+

SLA_INVF - Invert Linear Model +   +

+
+
ACTION: +
Invert a linear model of the type produced by the +sla_FITXY routine. +

CALL: +
CALL sla_INVF (FWDS,BKWDS,J) +

+

+
GIVEN: +
+
+ + + + + +
FWDSD(6)model coefficients
+

+
RETURNED: +
+
+ + + + + + + + + +
BKWDSD(6)inverse model
JIstatus: 0 = OK, -1 = no inverse
+

+
NOTES: +
+
1. +
The models relate two sets of $[\,x,y\,]$ coordinates as follows. +Naming the six elements of FWDS a,b,c,d,e & f, +where two sets of coordinates [x1,y1] and + $[x_{2},y_{2}\,]$ are related thus: +
x2 = a + bx1 + cy1
+ y2 = d + ex1 + fy1
+ The present routine generates a new set of coefficients + p,q,r,s,t & u (the array BKWDS) such that: +
x1 = p + qx2 + ry2
+ y1 = s + tx2 + uy2
+
2. +
Two successive calls to this routine will deliver a set + of coefficients equal to the starting values. +
3. +
To comply with the ANSI Fortran 77 standard, FWDS and BKWDS must + not be the same array. The routine is, in fact, coded + so as to work properly on the VAX and many other systems even + if this rule is violated, something that is not, however, + recommended. +
4. +
See also sla_FITXY, sla_PXY, sla_XY2XY, sla_DCMPF. +
+
+ +next + +up + +previous +
+ Next: SLA_KBJ - Select Epoch Prefix +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_INTIN - Decode an Integer Number +

+

+

+SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk +
+ + -- cgit