ISAJET/code/lstsq.F

   1 #include "isajet/pilot.h"
   2       SUBROUTINE LSTSQ(X,Y,NPT,A,B)
   3 C
   4 C          DO LEAST SQUARE FIT TO A STRAIGHT LINE Y=A+B*X
   5 C
   6 #include "isajet/itapes.inc"
   7       DIMENSION X(NPT),Y(NPT)
   8       SUM1=0
   9       SUM2=0
  10       SUM3=0
  11       SUM4=0
  12       DO 1 I=1,NPT
  13       SUM1=SUM1+X(I)
  14       SUM2=SUM2+Y(I)
  15       SUM3=SUM3+X(I)**2
  16       SUM4=SUM4+X(I)*Y(I)
  17     1 CONTINUE
  18       B=(SUM2*SUM1-SUM4*NPT)/(SUM1**2-SUM3*NPT)
  19       A=(SUM2-B*SUM1)/NPT
  20       RETURN
  21       END