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SUBROUTINE emcomp(Emu,Efreq,Ndays)
IMPLICIT NONE
c-----------------------------------------------------------------------
c Generate Easter means given a set of frequencies for Easter given
c by the user (Efreq).
c-----------------------------------------------------------------------
DOUBLE PRECISION ZERO
PARAMETER(ZERO=0D0)
c-----------------------------------------------------------------------
INTEGER kdate,Ndays,period,cmlnmo,julbeg,julend,ibeg,iend,itmp,
& juleas
DOUBLE PRECISION Emu,Efreq,tmp
DIMENSION Emu(2:4),Efreq(35),cmlnmo(13)
c-----------------------------------------------------------------------
DATA cmlnmo/0,31,59,90,120,151,181,212,243,273,304,334,365/
c-----------------------------------------------------------------------
c initialize easter mean for each month (Feb, March, April)
c-----------------------------------------------------------------------
DO period=2,4
Emu(period)=ZERO
c-----------------------------------------------------------------------
c compute percentage within easter window for each possible day of
c easter.
c-----------------------------------------------------------------------
DO kdate=1,35
c-----------------------------------------------------------------------
c Monthly Easter effect. Calculating Julian date of beginning and
c ending of present month
c-----------------------------------------------------------------------
julbeg=cmlnmo(period)+1
julend=cmlnmo(period+1)
c-----------------------------------------------------------------------
c Calculating Julian date of holidays and proportion of days in
c month which fall within the holiday window. Easter first.
c Computing beginning and ending dates of current month
c which overlap with holiday effect window
c-----------------------------------------------------------------------
juleas=cmlnmo(3)+22+kdate
ibeg=max(julbeg,juleas-ndays)
iend=min(julend,juleas-1)
c-----------------------------------------------------------------------
c Dividing days in current month which fall within window
c by length of window to computed proportion of days
c-----------------------------------------------------------------------
tmp=ZERO
IF(ibeg.le.iend)THEN
itmp=iend-ibeg+1
tmp=dble(itmp)/dble(ndays)
END IF
c-----------------------------------------------------------------------
c multiply percentage by frequency of occurance to get easter mean
c-----------------------------------------------------------------------
Emu(period)=Emu(period)+tmp*Efreq(kdate)
END DO
END DO
c-----------------------------------------------------------------------
RETURN
END
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