1 files changed, 53 insertions, 4 deletions
diff --git a/src/delta.c b/src/delta.c
index 6ca3794..79250e2 100644
--- a/src/delta.c
+++ b/src/delta.c
@@ -20,12 +20,49 @@
 
 /* xtract_delta.c: defines functions that extract a feature as a single value from more than one input vector */
 
+#include <math.h>
+
 #include "xtract/libxtract.h"
 
 int xtract_flux(const float *data, const int N, const void *argv , float *result){
 
+    return xtract_lnorm(data, N, argv, result);
 
-    return XTRACT_FEATURE_NOT_IMPLEMENTED;
+}
+
+int xtract_lnorm(const float *data, const int N, const void *argv , float *result){
+
+    int feature,
+        n,
+        type;
+
+    float order,
+          temp = 0.f;
+
+    order = *(float *)argv;
+    type = (int)*(float *)argv+1;
+
+    order = order > 0 ? order : 1.f;
+
+    switch(type){
+
+        case XTRACT_POSITIVE_SLOPE:
+            for(n = 0; n < N; n++){
+                temp = powf(data[n], order);
+                if(data[n] > 0)
+                    *result += temp;
+            }
+            break;
+        default:
+            for(n = 0; n < N; n++)
+                *result += powf(data[n], order);
+            break;
+
+    }
+
+    *result = powf(*result, 1.f / order);
+
+    return XTRACT_SUCCESS;
 
 }
 
@@ -41,9 +78,21 @@ int xtract_decay_time(const float *data, const int N, const void *argv, float *r
 
 }
 
-int xtract_delta_feature(const float *data, const int N, const void *argv, float *result){
+int xtract_difference_vector(const float *data, const int N, const void *argv, float *result){
 
-    return XTRACT_FEATURE_NOT_IMPLEMENTED;
+    float *frame1,
+          *frame2;
 
-}
+    int n;
 
+    n = N >> 1;
+
+    frame1 = data;
+    frame2 = data + n;
+
+    while(n--)
+        result[n] = frame1[n] - frame2[n];
+
+    return XTRACT_SUCCESS;
+
+}