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+.help pxy Jun99 "Slalib Package"
+.nf
+
+      SUBROUTINE slPXY (NP,XYE,XYM,COEFFS,XYP,XRMS,YRMS,RRMS)
+
+     - - - -
+      P X Y
+     - - - -
+
+  Given arrays of "expected" and "measured" [X,Y] coordinates, and a
+  linear model relating them (as produced by slFTXY), compute
+  the array of "predicted" coordinates and the RMS residuals.
+
+  Given:
+     NP       i        number of samples
+     XYE     d(2,np)   expected [X,Y] for each sample
+     XYM     d(2,np)   measured [X,Y] for each sample
+     COEFFS  d(6)      coefficients of model (see below)
+
+  Returned:
+     XYP     d(2,np)   predicted [X,Y] for each sample
+     XRMS     d        RMS in X
+     YRMS     d        RMS in Y
+     RRMS     d        total RMS (vector sum of XRMS and YRMS)
+
+  The model is supplied in the array COEFFS.  Naming the
+  elements of COEFF as follows:
+
+     COEFFS(1) = A
+     COEFFS(2) = B
+     COEFFS(3) = C
+     COEFFS(4) = D
+     COEFFS(5) = E
+     COEFFS(6) = F
+
+  the model is applied thus:
+
+     XP = A + B*XM + C*YM
+     YP = D + E*XM + F*YM
+
+  The residuals are (XP-XE) and (YP-YE).
+
+  If NP is less than or equal to zero, no coordinates are
+  transformed, and the RMS residuals are all zero.
+
+  See also slFTXY, slINVF, slXYXY, slDCMF
+
+  Called:  slXYXY
+
+  P.T.Wallace   Starlink   22 May 1996
+
+  Copyright (C) 1996 Rutherford Appleton Laboratory
+  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp