reorganize file structure

strut/derppval 2.m

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