### SLA_XY2XY

Apply Linear Model to an $\left[\phantom{\rule{0.3em}{0ex}}x,y\phantom{\rule{0.3em}{0ex}}\right]$

ACTION:
Transform one $\left[\phantom{\rule{0.3em}{0ex}}x,y\phantom{\rule{0.3em}{0ex}}\right]$ into another using a linear model of the type produced by the sla_FITXY routine.
CALL:
CALL sla_XY2XY (X1, Y1, COEFFS, X2, Y2)
##### GIVEN:
 X1,Y1 D $\left[\phantom{\rule{0.3em}{0ex}}x,y\phantom{\rule{0.3em}{0ex}}\right]$ before transformation COEFFS D(6) transformation coefficients (see note)

##### RETURNED:
 X2,Y2 D $\left[\phantom{\rule{0.3em}{0ex}}x,y\phantom{\rule{0.3em}{0ex}}\right]$ after transformation

NOTES:
(1)
The model relates two sets of $\left[\phantom{\rule{0.3em}{0ex}}x,y\phantom{\rule{0.3em}{0ex}}\right]$ coordinates as follows. Naming the six elements of COEFFS $a,b,c,d,e$ & $f$, the present routine performs the transformation:

${x}_{2}=a+b{x}_{1}+c{y}_{1}$
${y}_{2}=d+e{x}_{1}+f{y}_{1}$

(2)