PLearn 0.1
ClassErrorCostFunction.cc
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00001 // -*- C++ -*-
00002 
00003 // PLearn (A C++ Machine Learning Library)
00004 // Copyright (C) 1998 Pascal Vincent
00005 // Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio, Rejean Ducharme and University of Montreal
00006 // Copyright (C) 2001-2002 Nicolas Chapados, Ichiro Takeuchi, Jean-Sebastien Senecal
00007 // Copyright (C) 2002 Xiangdong Wang, Christian Dorion
00008 
00009 // Redistribution and use in source and binary forms, with or without
00010 // modification, are permitted provided that the following conditions are met:
00011 // 
00012 //  1. Redistributions of source code must retain the above copyright
00013 //     notice, this list of conditions and the following disclaimer.
00014 // 
00015 //  2. Redistributions in binary form must reproduce the above copyright
00016 //     notice, this list of conditions and the following disclaimer in the
00017 //     documentation and/or other materials provided with the distribution.
00018 // 
00019 //  3. The name of the authors may not be used to endorse or promote
00020 //     products derived from this software without specific prior written
00021 //     permission.
00022 // 
00023 // THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
00024 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00025 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
00026 // NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00027 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
00028 // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00029 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00030 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00031 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00032 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00033 // 
00034 // This file is part of the PLearn library. For more information on the PLearn
00035 // library, go to the PLearn Web site at www.plearn.org
00036 
00037 
00038 /* *******************************************************      
00039  * $Id: ClassErrorCostFunction.cc 5370 2006-04-12 15:27:55Z tihocan $
00040  * This file is part of the PLearn library.
00041  ******************************************************* */
00042 
00043 #include "ClassErrorCostFunction.h"
00044 #include <plearn/math/TMat_maths.h>
00045 
00046 namespace PLearn {
00047 using namespace std;
00048 
00049  
00050 // **** ClassErrorCostFunction ****
00051 
00052 PLEARN_IMPLEMENT_OBJECT(ClassErrorCostFunction, "Compute a classification cost function from ouput vector and target vector. ", "NO HELP");
00053 
00054 real ClassErrorCostFunction::evaluate(const Vec& output, const Vec& target) const
00055 {
00056     if(is_missing(output[0]) && ignore_missing_values && output.length()==1 )return MISSING_VALUE;
00057     if(output_is_classnum)
00058     {
00059         if(is_integer(output[0]))
00060             return fast_exact_is_equal(output[0], target[0]) ? 0 :1;
00061         else if(fast_exact_is_equal(target[0], 1.))
00062             return output[0]>0.5 ?0 :1;
00063         else // target[0]==0 or -1
00064             return output[0]<=0.5 ?0 :1;
00065     }
00066 
00067     if(output.length()==1) // we assume the sign of output indicates the chosen class 
00068     {
00069         if(target[0]>0)
00070             return output[0]>0 ?0. :1.;
00071         else
00072             return output[0]<0 ?0. :1.;
00073     }
00074     else // we assume output gives a score for each class
00075     {
00076         int trueclass;
00077         if(target.length()==1)
00078             trueclass = int(target[0]);
00079         else
00080             trueclass = argmax(target);
00081         return argmax(output)==trueclass ?0. :1.;
00082     }
00083 }
00084 
00085 void
00086 ClassErrorCostFunction::declareOptions(OptionList &ol)
00087 {
00088     declareOption(ol, "output_is_classnum", &ClassErrorCostFunction::output_is_classnum, OptionBase::buildoption, "Output of learner is class number");
00089     inherited::declareOptions(ol);
00090     declareOption(ol, "ignore_missing_values", &ClassErrorCostFunction::ignore_missing_values, OptionBase::buildoption, "When output is missing, do not compute cost and return MISSING_VALUE");
00091     inherited::declareOptions(ol);
00092 }
00093 
00094 
00095 
00096 } // end of namespace PLearn
00097 
00098 
00099 /*
00100   Local Variables:
00101   mode:c++
00102   c-basic-offset:4
00103   c-file-style:"stroustrup"
00104   c-file-offsets:((innamespace . 0)(inline-open . 0))
00105   indent-tabs-mode:nil
00106   fill-column:79
00107   End:
00108 */
00109 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=79 :
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