diff maths/MathUtilities.h @ 194:26daede606a8

Add L^p norms, doc, tests

--- a/maths/MathUtilities.h	Wed Oct 07 10:36:09 2015 +0100
+++ b/maths/MathUtilities.h	Wed Oct 07 11:14:16 2015 +0100
@@ -73,15 +73,22 @@
      */
     static double mod( double x, double y);
 
+    /**
+     * The alpha norm is the alpha'th root of the mean alpha'th power
+     * magnitude. For example if alpha = 2 this corresponds to the RMS
+     * of the input data, and when alpha = 1 this is the mean
+     * magnitude.
+     */
     static void	  getAlphaNorm(const double *data, int len, int alpha, double* ANorm);
+
+    /**
+     * The alpha norm is the alpha'th root of the mean alpha'th power
+     * magnitude. For example if alpha = 2 this corresponds to the RMS
+     * of the input data, and when alpha = 1 this is the mean
+     * magnitude.
+     */
     static double getAlphaNorm(const std::vector <double> &data, int alpha );
 
-    static void   circShift( double* data, int length, int shift);
-
-    static int	  getMax( double* data, int length, double* max = 0 );
-    static int	  getMax( const std::vector<double> &data, double* max = 0 );
-    static int    compareInt(const void * a, const void * b);
-
     enum NormaliseType {
         NormaliseNone,
         NormaliseUnitSum,
@@ -95,11 +102,34 @@
                           NormaliseType n = NormaliseUnitMax);
 
     /**
+     * Calculate the L^p norm of a vector. Equivalent to MATLAB's
+     * norm(data, p).
+     */
+    static double getLpNorm(const std::vector<double> &data,
+                            int p);
+
+    /**
+     * Normalise a vector by dividing through by its L^p norm. If the
+     * norm is below the given threshold, the unit vector for that
+     * norm is returned. p may be 0, in which case no normalisation
+     * happens and the data is returned unchanged.
+     */
+    static std::vector<double> normaliseLp(const std::vector<double> &data,
+                                           int p,
+                                           double threshold = 1e-6);
+    
+    /**
      * Threshold the input/output vector data against a moving-mean
      * average filter.
      */
     static void adaptiveThreshold(std::vector<double> &data);
 
+    static void   circShift( double* data, int length, int shift);
+
+    static int	  getMax( double* data, int length, double* max = 0 );
+    static int	  getMax( const std::vector<double> &data, double* max = 0 );
+    static int    compareInt(const void * a, const void * b);
+
     /** 
      * Return true if x is 2^n for some integer n >= 0.
      */