cubval.m

等高线拟合源代码（matlab源码）

% CUBVAL  : Calculation of spline value at given point               [f]
%
% CVAL = CUBVAL(X,A,B,C,D,V);
% Value evaluation of cubic spline given by X,A,B,C,D in V
%
%                               2          3
% CVAL = A + B (V-x ) + C (V-x ) + D (V-x )      with  x < V < x
%         k   k    k     k    k     k    k              k       k+1
%

function cval = cubval(n,x,a,b,c,d,v)

% c-code static int i = 1 %
n = length(x);
istart=1;
if n<2,
  error('N moet >= 2 ');
end
i=intone(x,n,v,istart);
dx = v- x(i);
cval = a(i)+dx*(b(i)+dx*(c(i)+d(i)*dx));
return