diff maths/MathUtilities.cpp @ 418:d583feeeed7a

Add L^p norms, doc, tests

--- a/maths/MathUtilities.cpp	Wed Oct 07 10:36:09 2015 +0100
+++ b/maths/MathUtilities.cpp	Wed Oct 07 11:14:16 2015 +0100
@@ -20,6 +20,7 @@
 #include <vector>
 #include <cmath>
 
+using namespace std;
 
 double MathUtilities::mod(double x, double y)
 {
@@ -56,7 +57,7 @@
     *ANorm = a;
 }
 
-double MathUtilities::getAlphaNorm( const std::vector <double> &data, int alpha )
+double MathUtilities::getAlphaNorm( const vector <double> &data, int alpha )
 {
     int i;
     int len = data.size();
@@ -66,7 +67,6 @@
     for( i = 0; i < len; i++)
     {
 	temp = data[ i ];
-		
 	a  += ::pow( fabs(temp), double(alpha) );
     }
     a /= ( double )len;
@@ -88,9 +88,9 @@
 {
     if (len == 0) return 0;
     
-    std::vector<double> scratch;
+    vector<double> scratch;
     for (int i = 0; i < len; ++i) scratch.push_back(src[i]);
-    std::sort(scratch.begin(), scratch.end());
+    sort(scratch.begin(), scratch.end());
 
     int middle = len/2;
     if (len % 2 == 0) {
@@ -126,7 +126,7 @@
     return retVal;
 }
 
-double MathUtilities::mean(const std::vector<double> &src,
+double MathUtilities::mean(const vector<double> &src,
                            int start,
                            int count)
 {
@@ -197,7 +197,7 @@
 	return index;
 }
 
-int MathUtilities::getMax( const std::vector<double> & data, double* pMax )
+int MathUtilities::getMax( const vector<double> & data, double* pMax )
 {
 	int index = 0;
 	int i;
@@ -286,7 +286,7 @@
     }
 }
 
-void MathUtilities::normalise(std::vector<double> &data, NormaliseType type)
+void MathUtilities::normalise(vector<double> &data, NormaliseType type)
 {
     switch (type) {
 
@@ -317,20 +317,46 @@
     }
 }
 
-void MathUtilities::adaptiveThreshold(std::vector<double> &data)
+double MathUtilities::getLpNorm(const vector<double> &data, int p)
+{
+    double tot = 0.0;
+    for (int i = 0; i < int(data.size()); ++i) {
+        tot += abs(pow(data[i], p));
+    }
+    return pow(tot, 1.0 / p);
+}
+
+vector<double> MathUtilities::normaliseLp(const vector<double> &data,
+                                               int p,
+                                               double threshold)
+{
+    int n = int(data.size());
+    if (n == 0 || p == 0) return data;
+    double norm = getLpNorm(data, p);
+    if (norm < threshold) {
+        return vector<double>(n, 1.0 / pow(n, 1.0 / p)); // unit vector
+    }
+    vector<double> out(n);
+    for (int i = 0; i < n; ++i) {
+        out[i] = data[i] / norm;
+    }
+    return out;
+}
+    
+void MathUtilities::adaptiveThreshold(vector<double> &data)
 {
     int sz = int(data.size());
     if (sz == 0) return;
 
-    std::vector<double> smoothed(sz);
+    vector<double> smoothed(sz);
 	
     int p_pre = 8;
     int p_post = 7;
 
     for (int i = 0; i < sz; ++i) {
 
-        int first = std::max(0,      i - p_pre);
-        int last  = std::min(sz - 1, i + p_post);
+        int first = max(0,      i - p_pre);
+        int last  = min(sz - 1, i + p_post);
 
         smoothed[i] = mean(data, first, last - first + 1);
     }