CAD／CAM技术及应用(11)

CAD／CAM技术及应用

%PPINTERP ppform interpretation.

switch method(1)

case 'n' % nearest

breaks = [xCol(1); ...

(xCol(1:end-1)+xCol(2:end))/2; ...

xCol(end)].';

coefs = yMat.';

pp = mkpp(breaks,coefs,ds);

case 'l' % linear

breaks = xCol.';

page1 = (diff(yMat)./repmat(diff(xCol),[1, prodDs])).'; page2 = (reshape(yMat(1:end-1,:),[n-1, prodDs])).'; coefs = cat(3,page1,page2);

pp = mkpp(breaks,coefs,ds);

case {'p', 'c'} % pchip and cubic

pp = pchip(xCol.',reshape(yMat.',[ds, n]));

case 's' % spline

pp = spline(xCol.',reshape(yMat.',[ds, n]));

case 'v' % v5cubic

b = diff(xCol);

if norm(diff(b),Inf) <= eps(norm(xCol,Inf))

% data are equally spaced

a = repmat(b,[1 prodDs]).';

yReorg = [3*yMat(1,:)-3*yMat(2,:)+yMat(3,:); ... yMat; ...

3*yMat(n,:)-3*yMat(n-1,:)+yMat(n-2,:)]; y1 = yReorg(1:end-3,:).';

y2 = yReorg(2:end-2,:).';

y3 = yReorg(3:end-1,:).';

y4 = yReorg(4:end,:).';

breaks = xCol.';

page1 = (-y1+3*y2-3*y3+y4)./(2*a.^3);

page2 = (2*y1-5*y2+4*y3-y4)./(2*a.^2);

page3 = (-y1+y3)./(2*a);

page4 = y2;

coefs = cat(3,page1,page2,page3,page4);

pp = mkpp(breaks,coefs,ds);

else

% data are not equally spaced

pp = spline(xCol.',reshape(yMat.',[ds, n]));

end

otherwise

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