MATLAB: Interpolation vector with a lot of duplicate values code on R2010a

interpolationunique

Please how i can use this code on Matlab R2010
y1 = [350 770 800 920 970 990 1020 1054 1080 1100];    
x1=[10 10 11 14 13 12 10 10 10 7];
x2 = [10 10 13 13 15 13 13 10 10 10];
[C,ia,idx] = unique(x1,'stable');
val = accumarray(idx,y1,[],@mean); %You could take something other than the mean.
your_vals = interp1(C,val,x2,'linear','extrap'); %see interp1() for other interpolation methods. Extrapolation is dangerous.
plot(x1,y1,'b*',x2,your_vals,'r+');
i get
??? Error using ==> unique
Unrecognized option

Best Answer

You can emulate the modern unique('stable') by:
function [AA, AI, BI] = UniqueStable(A)
% Equivalent to: unique(A(:), 'stable')
% Inptus: single, double (U)INT8/16/31/64, char
% Author: Jan Simon, Heidelberg 2017, License: CC BY-SA 3.0
nA = numel(A);
if nA == 0
   AA = [];
   AI = [];
   BI = [];
else
   [As, SV] = sort(A(:));
   if nargout == 1
      UV(SV) = ([true; diff(As) ~= 0]);
      AA     = A(UV);
     else  % Indices requested:
        UV      = ([true; diff(As) ~= 0]);
        UVs(SV) = UV;
        AI      = find(UVs).';
        AA      = A(UVs);
        % Complex creation of BI such that AA(BI) == A:
        v      = zeros(nA, 1);
        v(AI)  = 1:length(AI);    % Sequence related to AA
        vs     = v(SV);           % Sorted like A
        vf     = vs(vs ~= 0);     % Just the filled entries
        BI     = zeros(nA, 1);    % Pre-allocate
        BI(SV) = vf(cumsum(UV));  % Inflate multiple elements
     end
  end
[EDITED] Note: This is even faster than Matlab's unqiue(x, 'stable'):
x  = rand(1, 1e3);
f1 = @() UniqueStable(x);
f2 = @() unique(x, 'stable');
timeit(f1, 3)
timeit(f2, 3)
%    0.000191363010829893
%    0.000382956117288057
For 1e6 elements:
%    0.358884703612193
%    0.490294384698773
A version for cell strings: https://www.mathworks.com/matlabcentral/answers/45320-faster-function-than-unique-for-cell-arrays
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