1 files changed, 61 insertions, 0 deletions
diff --git a/gi/evaluation/conditional_entropy.py b/gi/evaluation/conditional_entropy.py
new file mode 100644
index 00000000..356d3b1d
--- /dev/null
+++ b/gi/evaluation/conditional_entropy.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python
+
+import sys, math, itertools, getopt
+
+def usage():
+    print >>sys.stderr, 'Usage:', sys.argv[0], '[-s slash_threshold] input-1 input-2'
+    sys.exit(0)
+
+optlist, args = getopt.getopt(sys.argv[1:], 'hs:')
+slash_threshold = None
+for opt, arg in optlist:
+    if opt == '-s':
+        slash_threshold = int(arg)
+    else:
+        usage()
+if len(args) != 2:
+    usage()
+
+ginfile = open(args[0])
+pinfile = open(args[1])
+
+# evaluating: H(G | P) = sum_{g,p} p(g,p) log { p(p) / p(g,p) }
+#                      = sum_{g,p} c(g,p)/N { log c(p) - log N - log c(g,p) + log N }
+#                      = 1/N sum_{g,p} c(g,p) { log c(p) - log c(g,p) }
+# where G = gold, P = predicted, N = number of events
+
+N = 0
+gold_frequencies = {}
+predict_frequencies = {}
+joint_frequencies = {}
+
+for gline, pline in itertools.izip(ginfile, pinfile):
+    gparts = gline.split('||| ')[1].split()
+    pparts = pline.split('||| ')[1].split()
+    assert len(gparts) == len(pparts)
+
+    for gpart, ppart in zip(gparts, pparts):
+        gtag = gpart.split(':',1)[1]
+        ptag = ppart.split(':',1)[1]
+
+        if slash_threshold == None or gtag.count('/') + gtag.count('\\') <= slash_threshold:
+            joint_frequencies.setdefault((gtag, ptag), 0)
+            joint_frequencies[gtag,ptag] += 1
+
+            predict_frequencies.setdefault(ptag, 0)
+            predict_frequencies[ptag] += 1
+
+            gold_frequencies.setdefault(gtag, 0)
+            gold_frequencies[gtag] += 1
+
+            N += 1
+
+hg2p = 0
+hp2g = 0
+for (gtag, ptag), cgp in joint_frequencies.items():
+    hp2g += cgp * (math.log(predict_frequencies[ptag], 2) - math.log(cgp, 2))
+    hg2p += cgp * (math.log(gold_frequencies[gtag], 2) - math.log(cgp, 2))
+hg2p /= N
+hp2g /= N
+
+print 'H(P|G)', hg2p, 'H(G|P)', hp2g, 'VI', hg2p + hp2g