improved edge correction for spike distance

Improvement following Eeros suggestions to use auxiliary spike at the edges
consistently with the corresponding corrected ISI intervals.

1 files changed, 35 insertions, 20 deletions

diff --git a/pyspike/cython/cython_distances.pyx b/pyspike/cython/cython_distances.pyx
index c4f2349..41baa60 100644
--- a/pyspike/cython/cython_distances.pyx
+++ b/pyspike/cython/cython_distances.pyx
@@ -176,6 +176,8 @@ def spike_distance_cython(double[:] t1, double[:] t2,
     cdef double t_p1, t_f1, t_p2, t_f2, dt_p1, dt_p2, dt_f1, dt_f2
     cdef double isi1, isi2, s1, s2
     cdef double y_start, y_end, t_last, t_current, spike_value
+    cdef double[:] t_aux1 = np.empty(2)
+    cdef double[:] t_aux2 = np.empty(2)
     
     spike_value = 0.0
 
@@ -184,19 +186,27 @@ def spike_distance_cython(double[:] t1, double[:] t2,
 
     with nogil: # release the interpreter to allow multithreading
         t_last = t_start
-        t_p1 = t_start
-        t_p2 = t_start
+        # t_p1 = t_start
+        # t_p2 = t_start
+        # auxiliary spikes for edge correction - consistent with first/last ISI 
+        t_aux1[0] = fmin(t_start, t1[0]-(t1[1]-t1[0]))
+        t_aux1[1] = fmax(t_end, t1[N1-1]+(t1[N1-1]-t1[N1-2]))
+        t_aux2[0] = fmin(t_start, t2[0]-(t2[1]-t2[0]))
+        t_aux2[1] = fmax(t_end, t2[N2-1]+(t2[N2-1]-t2[N2-2]))
+        t_p1 = t_start if (t1[0] == t_start) else t_aux1[0]
+        t_p2 = t_start if (t2[0] == t_start) else t_aux2[0]
         if t1[0] > t_start:
             # dt_p1 = t2[0]-t_start
             t_f1 = t1[0]
-            dt_f1 = get_min_dist_cython(t_f1, t2, N2, 0, t_start, t_end)
+            dt_f1 = get_min_dist_cython(t_f1, t2, N2, 0, t_aux2[0], t_aux2[1])
             isi1 = fmax(t_f1-t_start, t1[1]-t1[0])
             dt_p1 = dt_f1
-            s1 = dt_p1*(t_f1-t_start)/isi1
+            # s1 = dt_p1*(t_f1-t_start)/isi1
+            s1 = dt_p1
             index1 = -1
         else:
             t_f1 = t1[1]
-            dt_f1 = get_min_dist_cython(t_f1, t2, N2, 0, t_start, t_end)
+            dt_f1 = get_min_dist_cython(t_f1, t2, N2, 0, t_aux2[0], t_aux2[1])
             dt_p1 = 0.0
             isi1 = t1[1]-t1[0]
             s1 = dt_p1
@@ -204,14 +214,15 @@ def spike_distance_cython(double[:] t1, double[:] t2,
         if t2[0] > t_start:
             # dt_p1 = t2[0]-t_start
             t_f2 = t2[0]
-            dt_f2 = get_min_dist_cython(t_f2, t1, N1, 0, t_start, t_end)
+            dt_f2 = get_min_dist_cython(t_f2, t1, N1, 0, t_aux1[0], t_aux1[1])
             dt_p2 = dt_f2
             isi2 = fmax(t_f2-t_start, t2[1]-t2[0])
-            s2 = dt_p2*(t_f2-t_start)/isi2
+            # s2 = dt_p2*(t_f2-t_start)/isi2
+            s2 = dt_p2
             index2 = -1
         else:
             t_f2 = t2[1]
-            dt_f2 = get_min_dist_cython(t_f2, t1, N1, 0, t_start, t_end)
+            dt_f2 = get_min_dist_cython(t_f2, t1, N1, 0, t_aux1[0], t_aux1[1])
             dt_p2 = 0.0
             isi2 = t2[1]-t2[0]
             s2 = dt_p2
@@ -233,7 +244,7 @@ def spike_distance_cython(double[:] t1, double[:] t2,
                 if index1 < N1-1:
                     t_f1 = t1[index1+1]
                 else:
-                    t_f1 = t_end
+                    t_f1 = t_aux1[1]
                 t_curr =  t_p1
                 s2 = (dt_p2*(t_f2-t_p1) + dt_f2*(t_p1-t_p2)) / isi2
                 y_end = (s1*isi2 + s2*isi1)/isi_avrg_cython(isi1, isi2)
@@ -243,14 +254,16 @@ def spike_distance_cython(double[:] t1, double[:] t2,
                 # now the next interval start value
                 if index1 < N1-1:
                     dt_f1 = get_min_dist_cython(t_f1, t2, N2, index2,
-                                                t_start, t_end)
+                                                t_aux2[0], t_aux2[1])
                     isi1 = t_f1-t_p1
                     s1 = dt_p1
                 else:
                     dt_f1 = dt_p1
                     isi1 = fmax(t_end-t1[N1-1], t1[N1-1]-t1[N1-2])
                     # s1 needs adjustment due to change of isi1
-                    s1 = dt_p1*(t_end-t1[N1-1])/isi1
+                    # s1 = dt_p1*(t_end-t1[N1-1])/isi1
+                    # Eero's correction: no adjustment
+                    s1 = dt_p1
                 # s2 is the same as above, thus we can compute y2 immediately
                 y_start = (s1*isi2 + s2*isi1)/isi_avrg_cython(isi1, isi2)
             elif (index2 < N2-1) and (t_f1 > t_f2 or index1 == N1-1):
@@ -264,7 +277,7 @@ def spike_distance_cython(double[:] t1, double[:] t2,
                 if index2 < N2-1:
                     t_f2 = t2[index2+1]
                 else:
-                    t_f2 = t_end
+                    t_f2 = t_aux2[1]
                 t_curr = t_p2
                 s1 = (dt_p1*(t_f1-t_p2) + dt_f1*(t_p2-t_p1)) / isi1
                 y_end = (s1*isi2 + s2*isi1) / isi_avrg_cython(isi1, isi2)
@@ -274,14 +287,16 @@ def spike_distance_cython(double[:] t1, double[:] t2,
                 # now the next interval start value
                 if index2 < N2-1:
                     dt_f2 = get_min_dist_cython(t_f2, t1, N1, index1,
-                                                t_start, t_end)
+                                                t_aux1[0], t_aux1[1])
                     isi2 = t_f2-t_p2
                     s2 = dt_p2
                 else:
                     dt_f2 = dt_p2
                     isi2 = fmax(t_end-t2[N2-1], t2[N2-1]-t2[N2-2])
                     # s2 needs adjustment due to change of isi2
-                    s2 = dt_p2*(t_end-t2[N2-1])/isi2
+                    # s2 = dt_p2*(t_end-t2[N2-1])/isi2
+                    # Eero's correction: no adjustment
+                    s2 = dt_p2
                 # s1 is the same as above, thus we can compute y2 immediately
                 y_start = (s1*isi2 + s2*isi1)/isi_avrg_cython(isi1, isi2)
             else: # t_f1 == t_f2 - generate only one event
@@ -298,27 +313,27 @@ def spike_distance_cython(double[:] t1, double[:] t2,
                 if index1 < N1-1:
                     t_f1 = t1[index1+1]
                     dt_f1 = get_min_dist_cython(t_f1, t2, N2, index2,
-                                                t_start, t_end)
+                                                t_aux2[0], t_aux2[1])
                     isi1 = t_f1 - t_p1
                 else:
-                    t_f1 = t_end
+                    t_f1 = t_aux1[1]
                     dt_f1 = dt_p1
                     isi1 = fmax(t_end-t1[N1-1], t1[N1-1]-t1[N1-2])
                 if index2 < N2-1:
                     t_f2 = t2[index2+1]
                     dt_f2 = get_min_dist_cython(t_f2, t1, N1, index1,
-                                                t_start, t_end)
+                                                t_aux1[0], t_aux1[1])
                     isi2 = t_f2 - t_p2
                 else:
-                    t_f2 = t_end
+                    t_f2 = t_aux2[1]
                     dt_f2 = dt_p2
                     isi2 = fmax(t_end-t2[N2-1], t2[N2-1]-t2[N2-2])
             index += 1
             t_last = t_curr
         # isi1 = max(t_end-t1[N1-1], t1[N1-1]-t1[N1-2])
         # isi2 = max(t_end-t2[N2-1], t2[N2-1]-t2[N2-2])
-        s1 = dt_f1*(t_end-t1[N1-1])/isi1
-        s2 = dt_f2*(t_end-t2[N2-1])/isi2
+        s1 = dt_f1 # *(t_end-t1[N1-1])/isi1
+        s2 = dt_f2 # *(t_end-t2[N2-1])/isi2
         y_end = (s1*isi2 + s2*isi1) / isi_avrg_cython(isi1, isi2)
         spike_value += 0.5*(y_start + y_end) * (t_end - t_last)
     # end nogil