added distance based correlation function in matlab and java

matlab/distCorr.m

@@ -0,0 +1,41 @@
+% Autocorrelation for Points based on the distance between those points
+% data is the sensor data. one point per row. 
+% lag_size is the number of required lags
+function [corr, lag] = distCorr(data, lag_size)
+    
+    n = length(data);
+    
+    %if lag size is bigger as data, then use data length - 1
+    % -1 because the max. lag is -1 of the data length.. 
+    if(lag_size >= n)
+        lag_size = n - 1; %
+    end
+
+    %init 
+    corr = zeros(lag_size + 1, 1); % +1, because the first index is lag 0.
+    lag = (-lag_size:1:lag_size)';
+    
+    %mean shift and l2 normalization
+    %data = data - mean(data);
+    %data = data / norm(data);
+    
+    for j = 1:lag_size + 1 % +1, because the first index is lag 0.
+        dist = zeros(n - abs(j), 1);
+        idx = 1;
+        
+        for i = j:n
+            %x_i * x_i-(j-1)
+            dist(idx) = norm(data(i, :) - data(i-(j-1), :));
+            idx = idx + 1;
+        end
+        
+        corr(j) = geomean(dist);
+    end
+    
+    %mirror corr(2:512) and put it infront 
+    corr = [flipud(corr(2:end)); corr];
+    
+    %to [0, 1]
+    corr = ((corr .* -1) / max(corr)) + 1;
+    
+end