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<pre><span class="ruby-comment cmt"># File lib/rir/document.rb, line 78</span>
<span class="ruby-keyword kw">def</span> <span class="ruby-identifier">entropy</span>(<span class="ruby-identifier">s</span>)
<span class="ruby-identifier">en</span> = <span class="ruby-value">0</span><span class="ruby-value">.0</span>
<span class="ruby-identifier">counts</span> = <span class="ruby-keyword kw">self</span>.<span class="ruby-identifier">count_words</span>
<span class="ruby-identifier">s</span>.<span class="ruby-identifier">split</span>.<span class="ruby-identifier">each</span> <span class="ruby-keyword kw">do</span> <span class="ruby-operator">|</span><span class="ruby-identifier">w</span><span class="ruby-operator">|</span>
<span class="ruby-identifier">p_wi</span> = <span class="ruby-identifier">counts</span>[<span class="ruby-identifier">w</span>].<span class="ruby-identifier">to_f</span><span class="ruby-operator">/</span><span class="ruby-ivar">@words</span>.<span class="ruby-identifier">count</span>.<span class="ruby-identifier">to_f</span>
<span class="ruby-identifier">en</span> <span class="ruby-operator">+=</span> <span class="ruby-identifier">p_wi</span><span class="ruby-operator">*</span><span class="ruby-constant">Math</span>.<span class="ruby-identifier">log2</span>(<span class="ruby-identifier">p_wi</span>)
<span class="ruby-keyword kw">end</span>
<span class="ruby-identifier">en</span> <span class="ruby-operator">*=</span> <span class="ruby-value">-1</span>
<span class="ruby-identifier">en</span>
<span class="ruby-keyword kw">end</span></pre>
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