bayes.html

数据挖掘中的bayes算法,很好的代码

<pre>  Sex    Age Blood_pressure Drug bc
  male   20  normal         A    A
  female 73  normal         B    B
  female 37  high           A    A
  male   33  low            B    B
  female 48  high           A    A
  male   29  normal         A    A
  female 52  normal         B    B
  male   42  low            B    B
  male   61  normal         B    B
  female 30  normal         A    A
  female 26  low            B    B
  male   54  high           A    A
</pre>

<p>That is, the classification is perfect, which is not surprising
for such a simple example. The columns are neatly aligned because
of the <tt>-a</tt> option. Without it, there would only be a single
space between two column values.</p>

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<h3><a name="xmat">Computing a Confusion Matrix</a></h3>

<p>The classification quality can be inspected in more detail with
the program <tt>xmat</tt> (determine a confusion matrix, to be found
in the table package, see below):</p>

<pre>  xmat drug.cls</pre>

<p>This program reads the output of the program <tt>bcx</tt> and
computes a confusion matrix from two columns of this file. It uses
the last two columns by default (the last column for the x- and the
semi-last for the y-direction), which is fine for our example. Other
columns can be selected via the options <tt>-x</tt> and <tt>-y</tt>
followed by the name of the column that is to be used for the x- or
y-direction of the confusion matrix. The output of the program
<tt>xmat</tt>, which by default is written to the terminal, should
read like this:</p>

<pre>  confusion matrix for Drug vs. bc:
   no | value  |      1      2 | errors
  ----+--------+---------------+-------
    1 | A      |      6      0 |      0
    2 | B      |      0      6 |      0
  ----+--------+---------------+-------
      | errors |      0      0 |      0
</pre>

<p>In this matrix the x-direction corresponds to the column <tt>bc</tt>
and the y-direction to the column <tt>Drug</tt>. Since in our simple
example the classification is perfect, only the fields in the diagonal
differ from zero. If the classification is not perfect, the other
fields show what errors are made by the decision tree classifier.</p>

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<h3><a name="gendb">Generating a Database</a></h3>

<p>The program <tt>bcdb</tt> can be used to generate a database of
sample cases from a full or naive Bayes classifier. For example,
invoking it with</p>

<pre>  bcdb test.fbc test.tab</pre>

<p>generates a database with 1000 tuples from the full Bayes classifier
<tt>test.fbc</tt> that can be found in the directory <tt>ex</tt>.
The number of tuples to be generated can be changed with the option
<tt>-n#</tt>, where <tt>#</tt> is to be replaced by the desired number.
For other options call the program without any arguments.</p>

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<h3><a name="corr">Computing Covariances and
                   Correlation Coefficients</a></h3>

<p>The program <tt>corr</tt> can be used to computed covariances
and correlation coefficients. By invoking it with</p>

<pre>  correl -xvc iris.tab</pre>

<p>the expected values and standard deviations (option <tt>-x</tt>),
the covariances (option <tt>-v</tt>) and the correlation coefficients
(option <tt>-c</tt>) for the four numeric attributes of the well-known
iris data are computed. The output should look like this:</p>

<pre>   no | attribute    | exp. val. | std. dev.
   ---+--------------+-----------+----------
    1 | sepal_length |  5.843333 |  0.825301
    2 | sepal_width  |  3.057333 |  0.434411
    3 | petal_length |  3.758000 |  1.759404
    4 | petal_width  |  1.199333 |  0.759693

   covariance matrix
   no | attribute    |        1        2        3        4
   ---+--------------+------------------------------------
    1 | sepal_length |  0.68112 -0.04215  1.26582  0.51283
    2 | sepal_width  |           0.18871 -0.32746 -0.12083
    3 | petal_length |                    3.09550  1.28697
    4 | petal_width  |                             0.57713

   correlation coefficients
   no | attribute    |     1     2     3     4
   ---+--------------+------------------------
    1 | sepal_length |  1.00 -.118  .872  .818
    2 | sepal_width  |        1.00 -.428 -.366
    3 | petal_length |              1.00  .963
    4 | petal_width  |                    1.00
</pre>

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<h3><a name="copying">Copying</a></h3>

<p>bci/bcx/bcdb/corr -
   induce and execute full and naive Bayes classifiers<br>
   copyright &copy; 1996-2003 Christian Borgelt</p>

<p>These programs are free software; you can redistribute them
and/or modify them under the terms of the
<a href="http://www.fsf.org/copyleft/lesser.html">
GNU Lesser (Library) General Public License</a> as published by the
<a href="http://www.fsf.org">Free Software Foundation</a>.</p>

<p>These programs are distributed in the hope that they will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
<a href="http://www.fsf.org/copyleft/lesser.html">
GNU Lesser (Library) General Public License</a> for more details.</p>

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<h3><a name="download">Download</a></h3>

<p><a href="http://fuzzy.cs.uni-magdeburg.de/~borgelt/bayes.html">
Download page</a> with most recent version.</p>

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<h3><a name="contact">Contact</a></h3>

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<tr><td valign=top>Snail mail:</td><td width=10></td>
    <td><a href="http://fuzzy.cs.uni-magdeburg.de/~borgelt/index.html">
        Christian Borgelt</a><br>
        <a href="http://fuzzy.cs.uni-magdeburg.de/index.html">
        Working Group Neural Networks and Fuzzy Systems</a><br>
        <a href="http://www-iws.cs.uni-magdeburg.de/iws.html"> 
        Department of Knowledge Processing and Language Engineering</a><br>
        <a href="http://www.cs.uni-magdeburg.de/">
        School of Computer Science</a><br>
        <a href="http://www.uni-magdeburg.de/">
        Otto-von-Guericke-University of Magdeburg</a><br>
        Universit&auml;tsplatz 2<br>
        D-39106 Magdeburg<br>
        Germany</td></tr>
<tr><td valign=top>E-mail:</td><td></td>
    <td><a href="mailto:[e-mail]">
        [e-mail]</a><br>
        <a href="mailto:[e-mail]">
        [e-mail]</a></td></tr>
<tr><td>Phone:</td><td></td>
    <td>[phone]</td></tr>
<tr><td>Fax:</td><td></td>
    <td>[phone]</td></tr>
<tr><td>Office:</td><td></td>
    <td>29.015</td></tr>
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<address>&copy; 1999-2003
<a href="mailto:[e-mail]">Christian Borgelt</a>
</address>
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