??? Undefined function or method 'knn_dist' for input arguments of type 'double'. Error in ==> knn at 18 d = knn_dist(t​est_data(i​,:),train_​data);

for k = 1:k_upper
    for i = 1:num_test
        d = knn_dist(test_data(i,:),train_data);          
        [sort_d,index] = sort(d,1);                     
        k_d = sort_d(k);                                  
        [row,col] = find(d <= k_d);                       
        k_neigh = test_data(row,n);   
    end
end

Answer 1

[Geoff Hayes]

Sally - typically, the error message

 Undefined function or method 'knn_dist' for input arguments of type 'double

means that either the function knn_dist does not exist, or it isn't within your MATLAB search path, or you are not providing the correct inputs to this function (i.e. the function signature does not expect double inputs). It doesn't appear to be a built-in MATLAB function and the only reference to it (that I could find) was in the MATLAB File Exchange at https://www.mathworks.com/matlabcentral/fileexchange/35322-hidden-markov-modelling-of-contourlet-transforms-for-art-authentication/content/knn.m within the function

 function [C, IX, D] = knn(DM, idx, k, G)

 % Nearest neighbor classification on a pairwise distance matrix.
 %
 % Usage:
 %   [C, IX, D] = knn_dist(DM, idx, k, G)

The above seems to be a typo, since the function is called knn rather than knn_dist as indicated in the header. Is it from this submission that you are trying to use this function?

In the command line, type

 which -all knn_dist

and

 which -all knn

Do either return the path to a function?