--- /dev/null
+function Y=flix(D,x)
+% floating point index - interpolates data in case of non-integer indices
+%
+% Y=flix(D,x)
+% FLIX returns Y=D(x) if x is an integer
+% otherwise D(x) is interpolated from the neighbors D(ceil(x)) and D(floor(x))
+%
+% Applications:
+% (1) discrete Dataseries can be upsampled to higher sampling rate
+% (2) transformation of non-equidistant samples to equidistant samples
+% (3) [Q]=flix(sort(D),q*(length(D)+1)) calculates the q-quantile of data series D
+%
+% FLIX(D,x) is the same as INTERP1(D,X,'linear'); Therefore, FLIX might
+% become obsolete in future.
+%
+% see also: HIST2RES, Y2RES, PLOTCDF, INTERP1
+
+% $Id: flix.m 5090 2008-06-05 08:12:04Z schloegl $
+% Copyright (C) by 2001-2005,2008 Alois Schloegl <a.schloegl@ieee.org>
+% This is part of the TSA-toolbox see also:
+% http://www.dpmi.tu-graz.ac.at/schloegl/matlab/tsa/
+% http://octave.sf.net/
+%
+% This program is free software: you can redistribute it and/or modify
+% it under the terms of the GNU General Public License as published by
+% the Free Software Foundation, either version 3 of the License, or
+% (at your option) any later version.
+%
+% This program is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+D = D(:);
+Y = x;
+
+k1 = ((x >= 1) & (x <= size(D,1)));
+Y(~k1) = NaN;
+
+k = x - floor(x); % distance to next sample
+
+ix = ~k & k1; % find integer indices
+Y(ix) = D(x(ix)); % put integer indices
+
+ix = k & k1; % find non-integer indices
+
+Y(ix) = D(floor(x(ix))).*(1-k(ix)) + D(ceil(x(ix))).*k(ix);
+