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/node103.html | 170 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 170 insertions(+) create mode 100644 src/slalib/sun67.htx/node103.html (limited to 'src/slalib/sun67.htx/node103.html') diff --git a/src/slalib/sun67.htx/node103.html b/src/slalib/sun67.htx/node103.html new file mode 100644 index 0000000..4525328 --- /dev/null +++ b/src/slalib/sun67.htx/node103.html @@ -0,0 +1,170 @@ + + + + +SLA_FITXY - Fit Linear Model to Two Sets + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_FK425 - FK4 to FK5 +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_EVP - Earth Position & Velocity +

+

+

    +
+SLA_FITXY - Fit Linear Model to Two $[\,x,y\,]$ Sets +

+
+
ACTION: +
Fit a linear model to relate two sets of $[\,x,y\,]$ coordinates. +
CALL: +
CALL sla_FITXY (ITYPE,NP,XYE,XYM,COEFFS,J) +

+

+
GIVEN: +
+
+ + + + + + + + + + + + + + + + + +
ITYPEItype of model: 4 or 6 (note 1)
NPInumber of samples (note 2)
XYED(2,NP)expected $[\,x,y\,]$ for each sample
XYMD(2,NP)measured $[\,x,y\,]$ for each sample
+

+
RETURNED: +
+
+ + + + + + + + + + + + + + + + + + + + + + + + + +
COEFFSD(6)coefficients of model (note 3)
JIstatus:
0 = OK
-1 = illegal ITYPE
-2 = insufficient data
-3 = singular solution
+

+
NOTES: +
+
1. +
ITYPE, which must be either 4 or 6, selects the type of model +fitted. Both allowed ITYPE values produce a model COEFFS which +consists of six coefficients, namely the zero points and, for + each of XE and YE, the coefficient of XM and YM. For ITYPE=6, + all six coefficients are independent, modelling squash and shear + as well as origin, scale, and orientation. However, ITYPE=4 + selects the solid body rotation option; the model COEFFS + still consists of the same six coefficients, but now two of + them are used twice (appropriately signed). Origin, scale + and orientation are still modelled, but not squash or shear - + the units of X and Y have to be the same. +
2. +
For NC=4, NP must be at least 2. For NC=6, NP must be at + least 3. +
3. +
The model is returned in the array COEFFS. Naming the + six elements of COEFFS a,b,c,d,e & f, + the model transforms measured coordinates + $[x_{m},y_{m}\,]$ into expected coordinates + $[x_{e},y_{e}\,]$ as follows: +
xe = a + bxm + cym
+ ye = d + exm + fym
+ For the solid body rotation option (ITYPE=4), the + magnitudes of b and f, and of c and e, are equal. The + signs of these coefficients depend on whether there is a + sign reversal between [xe,ye] and [xm,ym]; + fits are performed + with and without a sign reversal and the best one chosen. +
4. +
Error status values J=-1 and -2 leave COEFFS unchanged; + if J=-3 COEFFS may have been changed. +
5. +
See also sla_PXY, sla_INVF, sla_XY2XY, sla_DCMPF. +
+
+ +next + +up + +previous +
+ Next: SLA_FK425 - FK4 to FK5 +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_EVP - Earth Position & Velocity +

+

+

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