[Positioner] Add similarity method "interval2"

owlps-positioner/cfg/owlps-positioner.conf

@@ -103,6 +103,13 @@ csv-file = /tmp/owlps-positioner.log
 #     packets in the measurement I are computed; the closest reference
 #     measurement R is the one with the highest number of packets in
 #     the interval [Im-Is, Im+Is].
+#   - interval2: Derived of the previous one, this algorithm
+#     computes the percent of packets in both the intervals
+#     [Im-0.674×Is, Im+0.674×Is] and [Im-Is, Im+Is].
+#     Assuming a normal distribution, we should find approximately
+#     50% of the packets in the first interval, and 68% in the second
+#     interval. The closest R is the one for which the percents of
+#     the two intervals are the closest to these theoretical scores.
 # The default is "mean".
 #ss-similarity = mean
 

owlps-positioner/src/measurement.cc

@@ -138,6 +138,28 @@ float Measurement::similarity(const Measurement &source) const
 
   if (algorithm == "interval")
     return 1 / nb_in_interval(source, get_std_deviation()) ;
+  /* Note: this score ranges from 0 (excluded) to 1 (obviously). */
+
+  if (algorithm == "interval2")
+    {
+      float std_dev = get_std_deviation() ;
+      float interval1 = nb_in_interval(source, 0.674 * std_dev) ;
+      float interval2 = nb_in_interval(source, std_dev) ;
+      /* Explanation: with a normal distribution, we normally have:
+       *   - 68% of the values within the interval
+       *     [mean-std.dev.;mean+std.dev.], and
+       *   - 50% of the value within the interval
+       *     [mean-.674*std.dev.;mean+.674*std.dev.] */
+
+      float percent1 = interval1 * 100 / source.get_nb_ss() ;
+      float percent2 = interval2 * 100 / source.get_nb_ss() ;
+
+      return (percent1 - 50) * (percent1 - 50) +
+             (percent2 - 68) * (percent2 - 68) ;
+      /* Note: this distance (score) ranges from 0 (with
+       * percent1==50 and percent2==68) to 7124 (with percent1
+       * and percent2==0). */
+    }
 
   throw bad_configuration(
     "Bad SS similarity algorithm name \""+ algorithm +"\"!") ;

owlps-positioner/src/userinterface.cc

@@ -242,7 +242,7 @@ void UserInterface::fill_positioning_options()
   ("positioning.ss-similarity",
    po::value<string>()->default_value(DEFAULT_SS_SIMILARITY),
    "Algorithm to calculate the similarity, in the signal strength space,"
-   " between two measurements. Allowed: mean, interval.")
+   " between two measurements. Allowed: mean, interval, interval2.")
   ("positioning.generate-reference-points",
    po::value<bool>()->default_value(false),
    "Generate reference points from the (auto)calibration requests"