updated ui added new features

third_party/codec2/octave/linreg.m

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+% linreg.m
+% David Rowe April 2015
+%
+% Based on:
+%    http://stackoverflow.com/questions/5083465/fast-efficient-least-squares-fit-algorithm-in-c
+%
+% finds y = mx + b to best fit n points x and y
+
+function [m b] = linreg(x,y,n)
+  sumx = 0.0;   % sum of x
+  sumx2 = 0.0;  % sum of x^2
+  sumxy = 0.0;  % sum of x * y
+  sumy = 0.0;   % sum of y
+  sumy2 = 0.0;  % sum of y**2
+
+  for i=1:n   
+    sumx  += x(i);       
+    sumx2 += x(i)^2;  
+    sumxy += x(i) * y(i);
+    sumy  += y(i);      
+    sumy2 += y(i)^2; 
+  end 
+
+  denom = (n * sumx2 - sumx*sumx);
+
+  if denom == 0
+    % singular matrix. can't solve the problem.
+    m = 0;
+    b = 0;
+  else
+    m = (n * sumxy  -  sumx * sumy) / denom;
+    b = (sumy * sumx2  -  sumx * sumxy) / denom;
+  end
+
+endfunction