[gnome-software: 5/7] ubuntu-reviews: Use gs_utils_get_wilson_rating()

[Richard Hughes <rhughes src gnome org>]

commit 3dcfc6fbc4bae08cd8c87579daf24adaaa16565b
Author: Richard Hughes <richard hughsie com>
Date:   Wed Jul 27 12:21:51 2016 +0100

    ubuntu-reviews: Use gs_utils_get_wilson_rating()

 src/plugins/gs-plugin-ubuntu-reviews.c |   65 ++-----------------------------
 1 files changed, 5 insertions(+), 60 deletions(-)
---
diff --git a/src/plugins/gs-plugin-ubuntu-reviews.c b/src/plugins/gs-plugin-ubuntu-reviews.c
index 30e845a..ea65c5d 100644
--- a/src/plugins/gs-plugin-ubuntu-reviews.c
+++ b/src/plugins/gs-plugin-ubuntu-reviews.c
@@ -186,65 +186,6 @@ get_review_stats_sqlite_cb (void *data,
        return 0;
 }
 
-static gdouble
-pnormaldist (gdouble qn)
-{
-       static gdouble b[11] = { 1.570796288,      0.03706987906,   -0.8364353589e-3,
-                               -0.2250947176e-3,  0.6841218299e-5,  0.5824238515e-5,
-                               -0.104527497e-5,   0.8360937017e-7, -0.3231081277e-8,
-                                0.3657763036e-10, 0.6936233982e-12 };
-       gdouble w1, w3;
-       int i;
-
-       if (qn < 0 || qn > 1)
-               return 0; // This is an error case
-       if (qn == 0.5)
-               return 0;
-
-       w1 = qn;
-       if (qn > 0.5)
-               w1 = 1.0 - w1;
-       w3 = -log (4.0 * w1 * (1.0 - w1));
-       w1 = b[0];
-       for (i = 1; i < 11; i++)
-               w1 = w1 + (b[i] * pow (w3, i));
-
-       if (qn > 0.5)
-               return sqrt (w1 * w3);
-       else
-               return -sqrt (w1 * w3);
-}
-
-static gdouble
-wilson_score (gdouble value, gint n, gdouble power)
-{
-       gdouble z, phat;
-
-       if (value == 0)
-               return 0;
-
-       z = pnormaldist (1 - power / 2);
-       phat = value / n;
-       return (phat + z * z / (2 * n) - z * sqrt ((phat * (1 - phat) + z * z / (4 * n)) / n)) / (1 + z * z / 
n);
-}
-
-static gint
-get_rating (gint64 one_star_count, gint64 two_star_count, gint64 three_star_count, gint64 four_star_count, 
gint64 five_star_count)
-{
-       gint n_ratings;
-
-       n_ratings = one_star_count + two_star_count + three_star_count + four_star_count + five_star_count;
-       if (n_ratings == 0)
-               return -1;
-
-       // Use a Wilson score which is a method of ensuring small numbers of ratings don't give high scores
-       // https://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval
-       return (((wilson_score (one_star_count, n_ratings, 0.1) * -2) +
-                (wilson_score (two_star_count, n_ratings, 0.1) * -1) +
-                (wilson_score (four_star_count, n_ratings, 0.1) * 1) +
-                (wilson_score (five_star_count, n_ratings, 0.1) * 2)) + 3) * 20 - 10;
-}
-
 static gboolean
 get_review_stats (GsPlugin *plugin,
                  const gchar *package_name,
@@ -275,7 +216,11 @@ get_review_stats (GsPlugin *plugin,
                return FALSE;
        }
 
-       *rating = get_rating (histogram.one_star_count, histogram.two_star_count, histogram.three_star_count, 
histogram.four_star_count, histogram.five_star_count);
+       *rating = gs_utils_get_wilson_rating (histogram.one_star_count,
+                                             histogram.two_star_count,
+                                             histogram.three_star_count,
+                                             histogram.four_star_count,
+                                             histogram.five_star_count);
        review_ratings[0] = 0;
        review_ratings[1] = histogram.one_star_count;
        review_ratings[2] = histogram.two_star_count;