/*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* Logistic.java
* Copyright (C) 2003-2012 University of Waikato, Hamilton, New Zealand
*
*/
package weka.classifiers.functions;
import weka.classifiers.Classifier;
import weka.classifiers.AbstractClassifier;
import weka.core.Aggregateable;
import weka.core.Capabilities;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.Optimization;
import weka.core.ConjugateGradientOptimization;
import weka.core.Option;
import weka.core.OptionHandler;
import weka.core.RevisionUtils;
import weka.core.TechnicalInformation;
import weka.core.TechnicalInformationHandler;
import weka.core.Utils;
import weka.core.WeightedInstancesHandler;
import weka.core.Capabilities.Capability;
import weka.core.TechnicalInformation.Field;
import weka.core.TechnicalInformation.Type;
import weka.filters.Filter;
import weka.filters.unsupervised.attribute.NominalToBinary;
import weka.filters.unsupervised.attribute.RemoveUseless;
import weka.filters.unsupervised.attribute.ReplaceMissingValues;
import java.util.Enumeration;
import java.util.Vector;
/**
<!-- globalinfo-start -->
* Class for building and using a multinomial logistic regression model with a ridge estimator.<br/>
* <br/>
* There are some modifications, however, compared to the paper of leCessie and van Houwelingen(1992): <br/>
* <br/>
* If there are k classes for n instances with m attributes, the parameter matrix B to be calculated will be an m*(k-1) matrix.<br/>
* <br/>
* The probability for class j with the exception of the last class is<br/>
* <br/>
* Pj(Xi) = exp(XiBj)/((sum[j=1..(k-1)]exp(Xi*Bj))+1) <br/>
* <br/>
* The last class has probability<br/>
* <br/>
* 1-(sum[j=1..(k-1)]Pj(Xi)) <br/>
* = 1/((sum[j=1..(k-1)]exp(Xi*Bj))+1)<br/>
* <br/>
* The (negative) multinomial log-likelihood is thus: <br/>
* <br/>
* L = -sum[i=1..n]{<br/>
* sum[j=1..(k-1)](Yij * ln(Pj(Xi)))<br/>
* +(1 - (sum[j=1..(k-1)]Yij)) <br/>
* * ln(1 - sum[j=1..(k-1)]Pj(Xi))<br/>
* } + ridge * (B^2)<br/>
* <br/>
* In order to find the matrix B for which L is minimised, a Quasi-Newton Method is used to search for the optimized values of the m*(k-1) variables. Note that before we use the optimization procedure, we 'squeeze' the matrix B into a m*(k-1) vector. For details of the optimization procedure, please check weka.core.Optimization class.<br/>
* <br/>
* Although original Logistic Regression does not deal with instance weights, we modify the algorithm a little bit to handle the instance weights.<br/>
* <br/>
* For more information see:<br/>
* <br/>
* le Cessie, S., van Houwelingen, J.C. (1992). Ridge Estimators in Logistic Regression. Applied Statistics. 41(1):191-201.<br/>
* <br/>
* Note: Missing values are replaced using a ReplaceMissingValuesFilter, and nominal attributes are transformed into numeric attributes using a NominalToBinaryFilter.
* <p/>
<!-- globalinfo-end -->
*
<!-- technical-bibtex-start -->
* BibTeX:
* <pre>
* @article{leCessie1992,
* author = {le Cessie, S. and van Houwelingen, J.C.},
* journal = {Applied Statistics},
* number = {1},
* pages = {191-201},
* title = {Ridge Estimators in Logistic Regression},
* volume = {41},
* year = {1992}
* }
* </pre>
* <p/>
<!-- technical-bibtex-end -->
*
<!-- options-start -->
* Valid options are: <p/>
*
* <pre> -D
* Turn on debugging output.</pre>
*
* <pre> -R <ridge>
* Set the ridge in the log-likelihood.</pre>
*
* <pre> -M <number>
* Set the maximum number of iterations (default -1, until convergence).</pre>
*
<!-- options-end -->
*
* @author Xin Xu (xx5@cs.waikato.ac.nz)
* @version $Revision: 9785 $
*/
public class Logistic extends AbstractClassifier
implements OptionHandler, WeightedInstancesHandler, TechnicalInformationHandler,
Aggregateable<Logistic> {
/** for serialization */
static final long serialVersionUID = 3932117032546553727L;
/** The coefficients (optimized parameters) of the model */
protected double [][] m_Par;
/** The data saved as a matrix */
protected double [][] m_Data;
/** The number of attributes in the model */
protected int m_NumPredictors;
/** The index of the class attribute */
protected int m_ClassIndex;
/** The number of the class labels */
protected int m_NumClasses;
/** The ridge parameter. */
protected double m_Ridge = 1e-8;
/** An attribute filter */
private RemoveUseless m_AttFilter;
/** The filter used to make attributes numeric. */
private NominalToBinary m_NominalToBinary;
/** The filter used to get rid of missing values. */
private ReplaceMissingValues m_ReplaceMissingValues;
/** Debugging output */
protected boolean m_Debug;
/** Log-likelihood of the searched model */
protected double m_LL;
/** The maximum number of iterations. */
private int m_MaxIts = -1;
/** Wether to use conjugate gradient descent rather than BFGS updates. */
private boolean m_useConjugateGradientDescent = false;
private Instances m_structure;
/**
* Returns a string describing this classifier
* @return a description of the classifier suitable for
* displaying in the explorer/experimenter gui
*/
public String globalInfo() {
return "Class for building and using a multinomial logistic "
+"regression model with a ridge estimator.\n\n"
+"There are some modifications, however, compared to the paper of "
+"leCessie and van Houwelingen(1992): \n\n"
+"If there are k classes for n instances with m attributes, the "
+"parameter matrix B to be calculated will be an m*(k-1) matrix.\n\n"
+"The probability for class j with the exception of the last class is\n\n"
+"Pj(Xi) = exp(XiBj)/((sum[j=1..(k-1)]exp(Xi*Bj))+1) \n\n"
+"The last class has probability\n\n"
+"1-(sum[j=1..(k-1)]Pj(Xi)) \n\t= 1/((sum[j=1..(k-1)]exp(Xi*Bj))+1)\n\n"
+"The (negative) multinomial log-likelihood is thus: \n\n"
+"L = -sum[i=1..n]{\n\tsum[j=1..(k-1)](Yij * ln(Pj(Xi)))"
+"\n\t+(1 - (sum[j=1..(k-1)]Yij)) \n\t* ln(1 - sum[j=1..(k-1)]Pj(Xi))"
+"\n\t} + ridge * (B^2)\n\n"
+"In order to find the matrix B for which L is minimised, a "
+"Quasi-Newton Method is used to search for the optimized values of "
+"the m*(k-1) variables. Note that before we use the optimization "
+"procedure, we 'squeeze' the matrix B into a m*(k-1) vector. For "
+"details of the optimization procedure, please check "
+"weka.core.Optimization class.\n\n"
+"Although original Logistic Regression does not deal with instance "
+"weights, we modify the algorithm a little bit to handle the "
+"instance weights.\n\n"
+"For more information see:\n\n"
+ getTechnicalInformation().toString() + "\n\n"
+"Note: Missing values are replaced using a ReplaceMissingValuesFilter, and "
+"nominal attributes are transformed into numeric attributes using a "
+"NominalToBinaryFilter.";
}
/**
* Returns an instance of a TechnicalInformation object, containing
* detailed information about the technical background of this class,
* e.g., paper reference or book this class is based on.
*
* @return the technical information about this class
*/
public TechnicalInformation getTechnicalInformation() {
TechnicalInformation result;
result = new TechnicalInformation(Type.ARTICLE);
result.setValue(Field.AUTHOR, "le Cessie, S. and van Houwelingen, J.C.");
result.setValue(Field.YEAR, "1992");
result.setValue(Field.TITLE, "Ridge Estimators in Logistic Regression");
result.setValue(Field.JOURNAL, "Applied Statistics");
result.setValue(Field.VOLUME, "41");
result.setValue(Field.NUMBER, "1");
result.setValue(Field.PAGES, "191-201");
return result;
}
/**
* Returns an enumeration describing the available options
*
* @return an enumeration of all the available options
*/
public Enumeration listOptions() {
Vector newVector = new Vector(4);
newVector.addElement(new Option("\tTurn on debugging output.",
"D", 0, "-D"));
newVector.addElement(new Option("\tUse conjugate gradient descent rather than BFGS updates.",
"C", 0, "-C"));
newVector.addElement(new Option("\tSet the ridge in the log-likelihood.",
"R", 1, "-R <ridge>"));
newVector.addElement(new Option("\tSet the maximum number of iterations"+
" (default -1, until convergence).",
"M", 1, "-M <number>"));
return newVector.elements();
}
/**
* Parses a given list of options. <p/>
*
<!-- options-start -->
* Valid options are: <p/>
*
* <pre> -D
* Turn on debugging output.</pre>
*
* <pre> -R <ridge>
* Set the ridge in the log-likelihood.</pre>
*
* <pre> -M <number>
* Set the maximum number of iterations (default -1, until convergence).</pre>
*
<!-- options-end -->
*
* @param options the list of options as an array of strings
* @throws Exception if an option is not supported
*/
public void setOptions(String[] options) throws Exception {
setDebug(Utils.getFlag('D', options));
setUseConjugateGradientDescent(Utils.getFlag('C', options));
String ridgeString = Utils.getOption('R', options);
if (ridgeString.length() != 0)
m_Ridge = Double.parseDouble(ridgeString);
else
m_Ridge = 1.0e-8;
String maxItsString = Utils.getOption('M', options);
if (maxItsString.length() != 0)
m_MaxIts = Integer.parseInt(maxItsString);
else
m_MaxIts = -1;
}
/**
* Gets the current settings of the classifier.
*
* @return an array of strings suitable for passing to setOptions
*/
public String [] getOptions() {
String [] options = new String [6];
int current = 0;
if (getDebug())
options[current++] = "-D";
if (getUseConjugateGradientDescent()) {
options[current++] = "-C";
}
options[current++] = "-R";
options[current++] = ""+m_Ridge;
options[current++] = "-M";
options[current++] = ""+m_MaxIts;
while (current < options.length)
options[current++] = "";
return options;
}
/**
* Returns the tip text for this property
* @return tip text for this property suitable for
* displaying in the explorer/experimenter gui
*/
public String debugTipText() {
return "Output debug information to the console.";
}
/**
* Sets whether debugging output will be printed.
*
* @param debug true if debugging output should be printed
*/
public void setDebug(boolean debug) {
m_Debug = debug;
}
/**
* Gets whether debugging output will be printed.
*
* @return true if debugging output will be printed
*/
public boolean getDebug() {
return m_Debug;
}
/**
* Returns the tip text for this property
* @return tip text for this property suitable for
* displaying in the explorer/experimenter gui
*/
public String useConjugateGradientDescentTipText() {
return "Use conjugate gradient descent rather than BFGS updates; faster for problems with many parameters.";
}
/**
* Sets whether conjugate gradient descent is used.
*
* @param useConjugateGradientDescent true if CGD is to be used.
*/
public void setUseConjugateGradientDescent(boolean useConjugateGradientDescent) {
m_useConjugateGradientDescent = useConjugateGradientDescent;
}
/**
* Gets whether to use conjugate gradient descent rather than BFGS updates.
*
* @return true if CGD is used
*/
public boolean getUseConjugateGradientDescent() {
return m_useConjugateGradientDescent;
}
/**
* Returns the tip text for this property
* @return tip text for this property suitable for
* displaying in the explorer/experimenter gui
*/
public String ridgeTipText() {
return "Set the Ridge value in the log-likelihood.";
}
/**
* Sets the ridge in the log-likelihood.
*
* @param ridge the ridge
*/
public void setRidge(double ridge) {
m_Ridge = ridge;
}
/**
* Gets the ridge in the log-likelihood.
*
* @return the ridge
*/
public double getRidge() {
return m_Ridge;
}
/**
* Returns the tip text for this property
* @return tip text for this property suitable for
* displaying in the explorer/experimenter gui
*/
public String maxItsTipText() {
return "Maximum number of iterations to perform.";
}
/**
* Get the value of MaxIts.
*
* @return Value of MaxIts.
*/
public int getMaxIts() {
return m_MaxIts;
}
/**
* Set the value of MaxIts.
*
* @param newMaxIts Value to assign to MaxIts.
*/
public void setMaxIts(int newMaxIts) {
m_MaxIts = newMaxIts;
}
private class OptEng extends Optimization {
OptObject m_oO = null;
private OptEng(OptObject oO) {
m_oO = oO;
}
protected double objectiveFunction(double[] x){
return m_oO.objectiveFunction(x);
}
protected double[] evaluateGradient(double[] x){
return m_oO.evaluateGradient(x);
}
public String getRevision() {
return RevisionUtils.extract("$Revision: 9785 $");
}
}
private class OptEngCG extends ConjugateGradientOptimization {
OptObject m_oO = null;
private OptEngCG(OptObject oO) {
m_oO = oO;
}
protected double objectiveFunction(double[] x){
return m_oO.objectiveFunction(x);
}
protected double[] evaluateGradient(double[] x){
return m_oO.evaluateGradient(x);
}
public String getRevision() {
return RevisionUtils.extract("$Revision: 9785 $");
}
}
private class OptObject {
/** Weights of instances in the data */
private double[] weights;
/** Class labels of instances */
private int[] cls;
/**
* Set the weights of instances
* @param w the weights to be set
*/
public void setWeights(double[] w) {
weights = w;
}
/**
* Set the class labels of instances
* @param c the class labels to be set
*/
public void setClassLabels(int[] c) {
cls = c;
}
/**
* Evaluate objective function
* @param x the current values of variables
* @return the value of the objective function
*/
protected double objectiveFunction(double[] x){
double nll = 0; // -LogLikelihood
int dim = m_NumPredictors+1; // Number of variables per class
for(int i=0; i<cls.length; i++){ // ith instance
double[] exp = new double[m_NumClasses-1];
int index;
for(int offset=0; offset<m_NumClasses-1; offset++){
index = offset * dim;
for(int j=0; j<dim; j++)
exp[offset] += m_Data[i][j]*x[index + j];
}
double max = exp[Utils.maxIndex(exp)];
double denom = Math.exp(-max);
double num;
if (cls[i] == m_NumClasses - 1) { // Class of this instance
num = -max;
} else {
num = exp[cls[i]] - max;
}
for(int offset=0; offset<m_NumClasses-1; offset++){
denom += Math.exp(exp[offset] - max);
}
nll -= weights[i]*(num - Math.log(denom)); // Weighted NLL
}
// Ridge: note that intercepts NOT included
for(int offset=0; offset<m_NumClasses-1; offset++){
for(int r=1; r<dim; r++)
nll += m_Ridge*x[offset*dim+r]*x[offset*dim+r];
}
return nll;
}
/**
* Evaluate Jacobian vector
* @param x the current values of variables
* @return the gradient vector
*/
protected double[] evaluateGradient(double[] x){
double[] grad = new double[x.length];
int dim = m_NumPredictors+1; // Number of variables per class
for(int i=0; i<cls.length; i++){ // ith instance
double[] num=new double[m_NumClasses-1]; // numerator of [-log(1+sum(exp))]'
int index;
for(int offset=0; offset<m_NumClasses-1; offset++){ // Which part of x
double exp=0.0;
index = offset * dim;
for(int j=0; j<dim; j++)
exp += m_Data[i][j]*x[index + j];
num[offset] = exp;
}
double max = num[Utils.maxIndex(num)];
double denom = Math.exp(-max); // Denominator of [-log(1+sum(exp))]'
for(int offset=0; offset<m_NumClasses-1; offset++){
num[offset] = Math.exp(num[offset] - max);
denom += num[offset];
}
Utils.normalize(num, denom);
// Update denominator of the gradient of -log(Posterior)
double firstTerm;
for(int offset=0; offset<m_NumClasses-1; offset++){ // Which part of x
index = offset * dim;
firstTerm = weights[i] * num[offset];
for(int q=0; q<dim; q++){
grad[index + q] += firstTerm * m_Data[i][q];
}
}
if(cls[i] != m_NumClasses-1){ // Not the last class
for(int p=0; p<dim; p++){
grad[cls[i]*dim+p] -= weights[i]*m_Data[i][p];
}
}
}
// Ridge: note that intercepts NOT included
for(int offset=0; offset<m_NumClasses-1; offset++){
for(int r=1; r<dim; r++)
grad[offset*dim+r] += 2*m_Ridge*x[offset*dim+r];
}
return grad;
}
}
/**
* Returns default capabilities of the classifier.
*
* @return the capabilities of this classifier
*/
public Capabilities getCapabilities() {
Capabilities result = super.getCapabilities();
result.disableAll();
// attributes
result.enable(Capability.NOMINAL_ATTRIBUTES);
result.enable(Capability.NUMERIC_ATTRIBUTES);
result.enable(Capability.DATE_ATTRIBUTES);
result.enable(Capability.MISSING_VALUES);
// class
result.enable(Capability.NOMINAL_CLASS);
result.enable(Capability.MISSING_CLASS_VALUES);
return result;
}
/**
* Builds the classifier
*
* @param train the training data to be used for generating the
* boosted classifier.
* @throws Exception if the classifier could not be built successfully
*/
public void buildClassifier(Instances train) throws Exception {
// can classifier handle the data?
getCapabilities().testWithFail(train);
// remove instances with missing class
train = new Instances(train);
train.deleteWithMissingClass();
// Replace missing values
m_ReplaceMissingValues = new ReplaceMissingValues();
m_ReplaceMissingValues.setInputFormat(train);
train = Filter.useFilter(train, m_ReplaceMissingValues);
// Remove useless attributes
m_AttFilter = new RemoveUseless();
m_AttFilter.setInputFormat(train);
train = Filter.useFilter(train, m_AttFilter);
// Transform attributes
m_NominalToBinary = new NominalToBinary();
m_NominalToBinary.setInputFormat(train);
train = Filter.useFilter(train, m_NominalToBinary);
// Save the structure for printing the model
m_structure = new Instances(train, 0);
// Extract data
m_ClassIndex = train.classIndex();
m_NumClasses = train.numClasses();
int nK = m_NumClasses - 1; // Only K-1 class labels needed
int nR = m_NumPredictors = train.numAttributes() - 1;
int nC = train.numInstances();
m_Data = new double[nC][nR + 1]; // Data values
int [] Y = new int[nC]; // Class labels
double [] xMean= new double[nR + 1]; // Attribute means
double [] xSD = new double[nR + 1]; // Attribute stddev's
double [] sY = new double[nK + 1]; // Number of classes
double [] weights = new double[nC]; // Weights of instances
double totWeights = 0; // Total weights of the instances
m_Par = new double[nR + 1][nK]; // Optimized parameter values
if (m_Debug) {
System.out.println("Extracting data...");
}
for (int i = 0; i < nC; i++) {
// initialize X[][]
Instance current = train.instance(i);
Y[i] = (int)current.classValue(); // Class value starts from 0
weights[i] = current.weight(); // Dealing with weights
totWeights += weights[i];
m_Data[i][0] = 1;
int j = 1;
for (int k = 0; k <= nR; k++) {
if (k != m_ClassIndex) {
double x = current.value(k);
m_Data[i][j] = x;
xMean[j] += weights[i]*x;
xSD[j] += weights[i]*x*x;
j++;
}
}
// Class count
sY[Y[i]]++;
}
if((totWeights <= 1) && (nC > 1))
throw new Exception("Sum of weights of instances less than 1, please reweight!");
xMean[0] = 0; xSD[0] = 1;
for (int j = 1; j <= nR; j++) {
xMean[j] = xMean[j] / totWeights;
if(totWeights > 1)
xSD[j] = Math.sqrt(Math.abs(xSD[j] - totWeights*xMean[j]*xMean[j])/(totWeights-1));
else
xSD[j] = 0;
}
if (m_Debug) {
// Output stats about input data
System.out.println("Descriptives...");
for (int m = 0; m <= nK; m++)
System.out.println(sY[m] + " cases have class " + m);
System.out.println("\n Variable Avg SD ");
for (int j = 1; j <= nR; j++)
System.out.println(Utils.doubleToString(j,8,4)
+ Utils.doubleToString(xMean[j], 10, 4)
+ Utils.doubleToString(xSD[j], 10, 4)
);
}
// Normalise input data
for (int i = 0; i < nC; i++) {
for (int j = 0; j <= nR; j++) {
if (xSD[j] != 0) {
m_Data[i][j] = (m_Data[i][j] - xMean[j]) / xSD[j];
}
}
}
if (m_Debug) {
System.out.println("\nIteration History..." );
}
double x[] = new double[(nR+1)*nK];
double[][] b = new double[2][x.length]; // Boundary constraints, N/A here
// Initialize
for(int p=0; p<nK; p++){
int offset=p*(nR+1);
x[offset] = Math.log(sY[p]+1.0) - Math.log(sY[nK]+1.0); // Null model
b[0][offset] = Double.NaN;
b[1][offset] = Double.NaN;
for (int q=1; q <= nR; q++){
x[offset+q] = 0.0;
b[0][offset+q] = Double.NaN;
b[1][offset+q] = Double.NaN;
}
}
OptObject oO = new OptObject();
oO.setWeights(weights);
oO.setClassLabels(Y);
Optimization opt = null;
if (m_useConjugateGradientDescent) {
opt = new OptEngCG(oO);
} else {
opt = new OptEng(oO);
}
opt.setDebug(m_Debug);
if(m_MaxIts == -1){ // Search until convergence
x = opt.findArgmin(x, b);
while(x==null){
x = opt.getVarbValues();
if (m_Debug)
System.out.println("First set of iterations finished, not enough!");
x = opt.findArgmin(x, b);
}
if (m_Debug)
System.out.println(" -------------<Converged>--------------");
}
else{
opt.setMaxIteration(m_MaxIts);
x = opt.findArgmin(x, b);
if(x==null) // Not enough, but use the current value
x = opt.getVarbValues();
}
m_LL = -opt.getMinFunction(); // Log-likelihood
// Don't need data matrix anymore
m_Data = null;
// Convert coefficients back to non-normalized attribute units
for(int i=0; i < nK; i++){
m_Par[0][i] = x[i*(nR+1)];
for(int j = 1; j <= nR; j++) {
m_Par[j][i] = x[i*(nR+1)+j];
if (xSD[j] != 0) {
m_Par[j][i] /= xSD[j];
m_Par[0][i] -= m_Par[j][i] * xMean[j];
}
}
}
}
/**
* Computes the distribution for a given instance
*
* @param instance the instance for which distribution is computed
* @return the distribution
* @throws Exception if the distribution can't be computed successfully
*/
public double [] distributionForInstance(Instance instance)
throws Exception {
m_ReplaceMissingValues.input(instance);
instance = m_ReplaceMissingValues.output();
m_AttFilter.input(instance);
instance = m_AttFilter.output();
m_NominalToBinary.input(instance);
instance = m_NominalToBinary.output();
// Extract the predictor columns into an array
double [] instDat = new double [m_NumPredictors + 1];
int j = 1;
instDat[0] = 1;
for (int k = 0; k <= m_NumPredictors; k++) {
if (k != m_ClassIndex) {
instDat[j++] = instance.value(k);
}
}
double [] distribution = evaluateProbability(instDat);
return distribution;
}
/**
* Compute the posterior distribution using optimized parameter values
* and the testing instance.
* @param data the testing instance
* @return the posterior probability distribution
*/
private double[] evaluateProbability(double[] data){
double[] prob = new double[m_NumClasses],
v = new double[m_NumClasses];
// Log-posterior before normalizing
for(int j = 0; j < m_NumClasses-1; j++){
for(int k = 0; k <= m_NumPredictors; k++){
v[j] += m_Par[k][j] * data[k];
}
}
v[m_NumClasses-1] = 0;
// Do so to avoid scaling problems
for(int m=0; m < m_NumClasses; m++){
double sum = 0;
for(int n=0; n < m_NumClasses-1; n++)
sum += Math.exp(v[n] - v[m]);
prob[m] = 1 / (sum + Math.exp(-v[m]));
}
return prob;
}
/**
* Returns the coefficients for this logistic model.
* The first dimension indexes the attributes, and
* the second the classes.
*
* @return the coefficients for this logistic model
*/
public double [][] coefficients() {
return m_Par;
}
/**
* Gets a string describing the classifier.
*
* @return a string describing the classifer built.
*/
public String toString() {
StringBuffer temp = new StringBuffer();
String result = "";
temp.append("Logistic Regression with ridge parameter of " + m_Ridge);
if (m_Par == null) {
return result + ": No model built yet.";
}
// find longest attribute name
int attLength = 0;
for (int i = 0; i < m_structure.numAttributes(); i++) {
if (i != m_structure.classIndex() &&
m_structure.attribute(i).name().length() > attLength) {
attLength = m_structure.attribute(i).name().length();
}
}
if ("Intercept".length() > attLength) {
attLength = "Intercept".length();
}
if ("Variable".length() > attLength) {
attLength = "Variable".length();
}
attLength += 2;
int colWidth = 0;
// check length of class names
for (int i = 0; i < m_structure.classAttribute().numValues() - 1; i++) {
if (m_structure.classAttribute().value(i).length() > colWidth) {
colWidth = m_structure.classAttribute().value(i).length();
}
}
// check against coefficients and odds ratios
for (int j = 1; j <= m_NumPredictors; j++) {
for (int k = 0; k < m_NumClasses - 1; k++) {
if (Utils.doubleToString(m_Par[j][k], 12, 4).trim().length() > colWidth) {
colWidth = Utils.doubleToString(m_Par[j][k], 12, 4).trim().length();
}
double ORc = Math.exp(m_Par[j][k]);
String t = " " + ((ORc > 1e10) ? "" + ORc : Utils.doubleToString(ORc, 12, 4));
if (t.trim().length() > colWidth) {
colWidth = t.trim().length();
}
}
}
if ("Class".length() > colWidth) {
colWidth = "Class".length();
}
colWidth += 2;
temp.append("\nCoefficients...\n");
temp.append(Utils.padLeft(" ", attLength) + Utils.padLeft("Class", colWidth) + "\n");
temp.append(Utils.padRight("Variable", attLength));
for (int i = 0; i < m_NumClasses - 1; i++) {
String className = m_structure.classAttribute().value(i);
temp.append(Utils.padLeft(className, colWidth));
}
temp.append("\n");
int separatorL = attLength + ((m_NumClasses - 1) * colWidth);
for (int i = 0; i < separatorL; i++) {
temp.append("=");
}
temp.append("\n");
int j = 1;
for (int i = 0; i < m_structure.numAttributes(); i++) {
if (i != m_structure.classIndex()) {
temp.append(Utils.padRight(m_structure.attribute(i).name(), attLength));
for (int k = 0; k < m_NumClasses-1; k++) {
temp.append(Utils.padLeft(Utils.doubleToString(m_Par[j][k], 12, 4).trim(), colWidth));
}
temp.append("\n");
j++;
}
}
temp.append(Utils.padRight("Intercept", attLength));
for (int k = 0; k < m_NumClasses-1; k++) {
temp.append(Utils.padLeft(Utils.doubleToString(m_Par[0][k], 10, 4).trim(), colWidth));
}
temp.append("\n");
temp.append("\n\nOdds Ratios...\n");
temp.append(Utils.padLeft(" ", attLength) + Utils.padLeft("Class", colWidth) + "\n");
temp.append(Utils.padRight("Variable", attLength));
for (int i = 0; i < m_NumClasses - 1; i++) {
String className = m_structure.classAttribute().value(i);
temp.append(Utils.padLeft(className, colWidth));
}
temp.append("\n");
for (int i = 0; i < separatorL; i++) {
temp.append("=");
}
temp.append("\n");
j = 1;
for (int i = 0; i < m_structure.numAttributes(); i++) {
if (i != m_structure.classIndex()) {
temp.append(Utils.padRight(m_structure.attribute(i).name(), attLength));
for (int k = 0; k < m_NumClasses-1; k++) {
double ORc = Math.exp(m_Par[j][k]);
String ORs = " " + ((ORc > 1e10) ? "" + ORc : Utils.doubleToString(ORc, 12, 4));
temp.append(Utils.padLeft(ORs.trim(), colWidth));
}
temp.append("\n");
j++;
}
}
return temp.toString();
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 9785 $");
}
protected int m_numModels = 0;
/**
* Aggregate an object with this one
*
* @param toAggregate the object to aggregate
* @return the result of aggregation
* @throws Exception if the supplied object can't be aggregated for some
* reason
*/
@Override
public Logistic aggregate(Logistic toAggregate) throws Exception {
if (m_numModels == Integer.MIN_VALUE) {
throw new Exception(
"Can't aggregate further - model has already been "
+ "aggregated and finalized");
}
if (m_Par == null) {
throw new Exception("No model built yet, can't aggregate");
}
if (!m_structure.equalHeaders(toAggregate.m_structure)) {
throw new Exception("Can't aggregate - data headers dont match: "
+ m_structure.equalHeadersMsg(toAggregate.m_structure));
}
for (int i = 0; i < m_Par.length; i++) {
for (int j = 0; j < m_Par[i].length; j++) {
m_Par[i][j] += toAggregate.m_Par[i][j];
}
}
m_numModels++;
return this;
}
/**
* Call to complete the aggregation process. Allows implementers to do any
* final processing based on how many objects were aggregated.
*
* @throws Exception if the aggregation can't be finalized for some reason
*/
@Override
public void finalizeAggregation() throws Exception {
if (m_numModels == Integer.MIN_VALUE) {
throw new Exception("Aggregation has already been finalized");
}
if (m_numModels == 0) {
throw new Exception("Unable to finalize aggregation - " +
"haven't seen any models to aggregate");
}
for (int i = 0; i < m_Par.length; i++) {
for (int j = 0; j < m_Par[i].length; j++) {
m_Par[i][j] /= (m_numModels + 1);
}
}
// aggregation complete
m_numModels = Integer.MIN_VALUE;
}
/**
* Main method for testing this class.
*
* @param argv should contain the command line arguments to the
* scheme (see Evaluation)
*/
public static void main(String [] argv) {
runClassifier(new Logistic(), argv);
}
}