1 files changed, 80 insertions, 0 deletions
diff --git a/tf-idf b/tf-idf
new file mode 100755
index 0000000..3edaaf8
--- /dev/null
+++ b/tf-idf
@@ -0,0 +1,80 @@
+#!/usr/bin/env ruby
+
+require 'trollop'
+
+
+# returns word='raw frequency' for a single document
+def tf(d, stopwords=[])
+  v = {}; v.default = 0
+  d.uniq.each { |i|
+   next if stopwords.include? i
+   v[i] = d.count(i).to_f
+  }
+  return v
+end
+
+# smoothes raw frequencies
+def ntf(w, a=0.4)
+  max = w.values.max.to_f
+  w.each_pair { |k,v|
+    w[k] = a + (1-a)*(v/max)
+  }
+end
+
+# returns idf value for each word in vocab
+def idf(collection)
+  vocab = collection.values.flatten.uniq
+  n = collection.size.to_f
+  idf = {}
+  vocab.each { |i|
+    df = collection.values.flatten.count i
+    idf[i] = Math.log(n/df)
+  }
+  return idf
+end
+
+def main
+  opts = Trollop::options do
+    opt :docs, "input files (documents)", :type => :strings, :required => true
+    opt :filter_stopwords, "filter stopwords (give file)", :type => :string
+    opt :one_item_per_line, "one item per line (allow multi-word items)", :type => :bool
+    opt :ntf, "length-normalize tf values", :type => :bool
+    opt :idf, "weight tf by idf", :type => :bool
+  end
+
+  stopwords = []
+  if opts[:filter_stopwords]
+    stopwords = File.new('stop.txt.utf8', 'r').readlines.map{|i| i.split('|').first.strip}.reject{|i|i==''}
+  end
+
+  docs = {} # fn => [words...]
+  opts[:docs].each { |i|
+    if opts[:one_item_per_line]
+      docs[i] = File.new(i, 'r').readlines.map{|i| i.strip}
+    else
+     docs[i] = File.new(i, 'r').read.split(/\s/).map{|i| i.strip}
+    end
+  }
+
+  idf_values = idf docs
+
+  docs.each_pair { |name, words|
+    just_tf = tf(words)
+    just_tf = ntf(just_tf) if opts[:ntf]
+    tf_idf = {}; tf_idf.default = 0.0
+    if opts[:idf]
+      just_tf.each_pair { |word,f|
+        tf_idf[word] = idf_values[word] * f
+      }
+    else
+      tf_idf = just_tf
+    end
+    docs[name] = tf_idf
+  }
+
+  docs.each { |i| puts i.to_s }
+end
+
+
+main
+