49 lines
1.4 KiB
Matlab
Executable File
49 lines
1.4 KiB
Matlab
Executable File
function v=derppval(pp,xx)
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%PPVAL Evaluate piecewise polynomial.
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% V = PPVAL(PP,XX) returns the value at the points XX of the
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% piecewise polynomial contained in PP, as constructed by SPLINE
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% (or MKPP).
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%
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% Revised by B.A. Broughton on 10/01/1999 to calculate the derivative
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% for a pre-fitted cubic spline in the points xx
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%
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% See also SPLINE.
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% Carl de Boor 7-2-86
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% Revised 10-14-97 CB to speed up locating points in mesh (as in
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% PPUAL) and to handle vector-valued functions.
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% Copyright (c) 1984-98 by The MathWorks, Inc.
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% $Revision: 5.8 $ $Date: 1997/11/21 23:41:00 $
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[mx,nx] = size(xx); lx = mx*nx; xs = reshape(xx,1,lx);
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% if necessary, sort xx
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tosort=0;
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if any(diff(xs)<0)
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tosort=1;[xs,ix]=sort(xs);
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end
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% take apart pp
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[x,c,l,k,d]=unmkpp(pp);
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% for each data point, compute its breakpoint interval
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[ignored,index] = sort([x(1:l) xs]);
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index = max([find(index>l)-(1:lx);ones(1,lx)]);
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% now go to local coordinates ...
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xs = xs-x(index);
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if d>1 % ... replicate xs and index in case pp is vector-valued ...
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xs = reshape(xs(ones(d,1),:),1,d*lx);
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index = d*index; temp = [-d:-1].';
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index = reshape(1+index(ones(d,1),:)+temp(:,ones(1,lx)), d*lx, 1 );
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end
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% ... and apply nested multiplication to get derivative:
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v = 3*c(index,1).';
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for i=2:k-1
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v = xs.*v + (4-i)*c(index,i).';
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end
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v = reshape(v,d,lx);
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if tosort>0, v(:,ix) = v; end
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v = reshape(v,d*mx,nx);
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