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subroutine intp(x,xd,yd,n,nc,y)
c!purpose
c linear interpolation computes y=F(x) for f a tabulated function
c from R to R^n
c!parameters
c x : x given point
c xd : vector (nc) of abscissae mesh points (xd(i+1)>=xd(i))
c yd : matrix (nc x n): yd(i,j)=Fj(x(i))
c n : dimension of F image
c returned values
c y : vector (n) :interpolated value of F(x)
c!remarks
c if x<=xd(1) y=yd(1,:)
c if x>=xd(nc) y=yd(nc,:)
c!origin
c Pejman GOHARI 1996
c!
c Copyright INRIA
double precision x,xd(*),y(*),yd(nc,*)
integer n,nc
c
if (nc.eq.1) then
call dcopy(n,yd(1,1),nc,y,1)
elseif(x.ge.xd(nc)) then
call dcopy(n,yd(nc,1),nc,y,1)
elseif(x.le.xd(1)) then
call dcopy(n,yd(1,1),nc,y,1)
else
c find x interval
do 10 i=1,nc
if (x.lt.xd(i)) then
inter=i-1
goto 20
endif
10 continue
20 continue
c
c compute interpolated y
c
if (xd(inter+1).eq.xd(inter)) then
call dcopy(n,yd(inter,1),nc,y,1)
else
do 40 i=1,n
y(i)=yd(inter,i)+
& (x-xd(inter))*((yd(inter+1,i)-yd(inter,i))/
& (xd(inter+1)-xd(inter)))
40 continue
endif
endif
end
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