https://github.com/cran/fields
Tip revision: 6769ffc81115fbf0bf7d9c566cf7ac81be0049dc authored by Doug Nychka on 25 July 2005, 00:00:00 UTC
version 3.04
version 3.04
Tip revision: 6769ffc
gcvcss.f
subroutine gcvcss(n,x,y,wt,c,offset,nstep,maxit,
- hmin, hmax,hopt,vopt,
- tropt,mxstep,fout,
- ierr)
implicit double precision (a-h,o-z)
real*8 fout(mxstep,3)
real*8 x(n),y(n),wt(n)
real*8 hopt,vopt,trace, hmin,hmax
data tau,tausq/.6180339d0,.3819660d0/
**** coarse search in bandwidth h: this search feeds (hl,hr) to golden search
c compute range for coarse search
if (mxstep .lt. nstep) then
ierr=10
return
endif
c
C rough idea of lambda serach grid
c
if( hmin.ge.hmax) then
xmin= x(1)
xmax= x(1)
do 500 i=1,n
if( x(i).lt.xmin) xmin=x(i)
if( x(i).gt.xmax) xmax=x(i)
500 continue
range = xmax- xmin
xnobs=n
c** c= cost value on GCV function there is a pole at trp=2+ nobs/c
trp=(Xnobs-offset)*.97/c
if( trp.le.2.0) then
c** offset is too big!
ierr=11
return
endif
hmin= -0.755762d0 + 0.706693d0*log(xnobs)
* + 0.01884722d0*(log(xnobs)**2) -4.918114d0*log(trp)
* + 0.0879931d0*(log(trp)**2)
c write(*,*) hmin, range, xnobs
hmin= hmin + log(range)*3.d0-log(xnobs)
trp=2.01d0
hmax= -0.755762d0 + 0.706693d0*log(xnobs)
* + 0.01884722d0*(log(xnobs)**2) -4.918114d0*log(trp)
* + 0.0879931d0*(log(trp)**2)
hmax= hmax + log(range)*3.d0-log(xnobs)
endif
hstep=(hmax-hmin)/(nstep-1)
do 3 j=0,nstep-1
h=hmin+j*hstep
gcvh= gcvfc(h,n,x,y,wt,c,offset,trace)
fout(j+1,1)=h
fout(j+1,2)=trace
fout(j+1,3)=gcvh
if ((gcvh .lt. gcvmin) .or. (j .eq. 0)) then
hopt=h
best=h
gcvmin=gcvh
trbest=trace
endif
c write(*,5000) h, trace,gcvh
5000 format(5e12.4)
c
3 continue
c
c write(*,*) ' Crude search of optimal h completed'
c
**** fast return if crude search minimum gcv is hmin or hmax
hopt= best
vopt=gcvmin
tropt=trbest
if( (best.eq.hmin) .or. (best.eq.h) ) then
ierr=-1
return
endif
c**** start values for golden search
hl=best-hstep
hr=best+hstep
*** Golden section search for min gcv on interval (hl,hr)--maxit(=15) iterations
*** gcv(h) must be quasiconvex on initial interval (hl,hr).
*** On return, h=abscissa of minimum, v=gcv(h)=actual minimum achieved.
*** Interval of uncertainty is (hl,hr), hl <= hlm <= hrm <= hr.
gcvhl=gcvfc(hl,n,x,y,wt,c,offset,trace)
gcvhr=gcvfc(hr,n,x,y,wt,c,offset,trace)
hlm=hl*tau+hr*tausq
hrm=hl+hr-hlm
gcvhlm=gcvfc(hlm,n,x,y,wt,c,offset,trchlm)
gcvhrm=gcvfc(hrm,n,x,y,wt,c,offset,trchrm)
do 5 it=1,maxit
if( gcvhlm .ge. gcvhrm ) then
if (gcvhl .lt. gcvhlm) then
err= gcvhl/gcvhlm
c write(*,10) it,err,hl,hlm
ierr=2
return
endif
c
hl=hlm
gcvhl=gcvhlm
hlm=hrm
hrm=hrm+(hrm-hl)*tau
gcvhlm=gcvhrm
gcvhrm=gcvfc(hrm,n,x,y,wt,c,offset,trchrm)
else
if (gcvhr .lt. gcvhrm) then
err= gcvhrm/gcvhr
c write(*,11) it,err,hr,hrm
ierr=2
return
endif
c
hr=hrm
gcvhr=gcvhrm
hrm=hlm
hlm=hlm+(hlm-hr)*tau
gcvhrm=gcvhlm
gcvhlm=gcvfc(hlm,n,x,y, wt,c,offset,trchlm)
endif
5 continue
**** finished -- take the best h so far
if( gcvhlm .ge. gcvhrm) then
hopt=hrm
vopt=gcvhrm
tropt=trchrm
else
hopt=hlm
vopt=gcvhlm
tropt=trchlm
endif
c
10 format(' gcv(h) is NOT quasiconvex ',/,
- ' iter,error,hl,hlm: ',I4,e15.5,2e15.5)
11 format(' gcv(h) is NOT quasiconvex ',/,
- ' iter,error,hr,hrm: ',I4,e15.5,2e15.5)
c
c
c write(*,*) 'hopt', hopt
return
end