@Override
public RealVector computeSyntheticValues(SampleIterator it) {
it.reset();
Sample sample = it.next();
int inputDim = sample.getEncodedInput().getDimension();
int outputDim = sample.getEncodedOutput().getDimension();
RealVector v = new ArrayRealVector(outputDim);
for (int out = 0; out < outputDim; out++) {
it.reset();
double eta = generalizedCorrelationRatio(it, inputDim, out);
if (eta < 0) return null;
v.setEntry(out, eta);
}
return v;
}
@Override
public RealMatrix computeIOCorrelationMatrix(SampleIterator it) {
it.reset();
Sample sample = it.next();
int inputDim = sample.getEncodedInput().getDimension();
int outputDim = sample.getEncodedOutput().getDimension();
RealMatrix M = new Array2DRowRealMatrix(inputDim, outputDim);
for (int i = 0; i < inputDim; i++) {
for (int j = 0; j < outputDim; j++) {
it.reset();
M.setEntry(i, j, correlationRatio(it, i, j));
}
}
return M;
}
private double correlationRatio(SampleIterator it, int in, int out) {
Map<Double, Integer> n_y = new HashMap<>();
Map<Double, RealVector> x_y = new HashMap<>();
RealVector x = new ArrayRealVector();
for (int i = 0; i < maxSamples && it.hasNext(); i++) {
Sample sample = it.next();
double input = sample.getEncodedInput().getEntry(in);
double output = sample.getEncodedOutput().getEntry(out);
if (!n_y.containsKey(output)) {
n_y.put(output, 0);
x_y.put(output, new ArrayRealVector());
}
input = injectNoise(input);
n_y.put(output, n_y.get(output) + 1);
x_y.put(output, x_y.get(output).append(input));
x = x.append(input);
}
double x_mean = StatUtils.mean(x.toArray());
Map<Double, Double> x_y_mean = new HashMap<>();
for (Entry<Double, RealVector> entry : x_y.entrySet()) {
x_y_mean.put(entry.getKey(), StatUtils.mean(entry.getValue().toArray()));
}
double numerator = 0;
for (double key : n_y.keySet()) {
numerator += n_y.get(key) * (x_y_mean.get(key) - x_mean) * (x_y_mean.get(key) - x_mean);
}
double denominator = 0;
for (double e : x.toArray()) {
denominator += (e - x_mean) * (e - x_mean);
}
double eta = denominator == 0 ? 0 : Math.sqrt(numerator / denominator);
return eta;
}
private double generalizedCorrelationRatio(SampleIterator it, int inputDim, int out) {
Map<Double, Integer> n_y = new HashMap<>();
Map<Double, MultivariateSummaryStatistics> stat_y = new HashMap<>();
List<RealMatrix> x = new ArrayList<>();
MultivariateSummaryStatistics stat = new MultivariateSummaryStatistics(inputDim, unbiased);
for (int i = 0; i < maxSamples && it.hasNext(); i++) {
Sample sample = it.next();
double[] input = sample.getEncodedInput().toArray();
double output = sample.getEncodedOutput().getEntry(out);
if (!n_y.containsKey(output)) {
n_y.put(output, 0);
stat_y.put(output, new MultivariateSummaryStatistics(inputDim, unbiased));
}
injectNoise(input);
n_y.put(output, n_y.get(output) + 1);
stat_y.get(output).addValue(input);
x.add(new Array2DRowRealMatrix(input));
stat.addValue(input);
}
RealMatrix x_sum = new Array2DRowRealMatrix(stat.getSum());
Map<Double, RealMatrix> x_y_sum = new HashMap<>();
for (Entry<Double, MultivariateSummaryStatistics> entry : stat_y.entrySet()) {
x_y_sum.put(entry.getKey(), new Array2DRowRealMatrix(entry.getValue().getSum()));
}
RealMatrix H = new Array2DRowRealMatrix(inputDim, inputDim);
RealMatrix temp = new Array2DRowRealMatrix(inputDim, inputDim);
for (double key : n_y.keySet()) {
temp =
temp.add(
x_y_sum
.get(key)
.multiply(x_y_sum.get(key).transpose())
.scalarMultiply(1.0 / n_y.get(key)));
}
H = temp.subtract(x_sum.multiply(x_sum.transpose()).scalarMultiply(1.0 / x.size()));
RealMatrix E = new Array2DRowRealMatrix(inputDim, inputDim);
for (RealMatrix m : x) {
E = E.add(m.multiply(m.transpose()));
}
E = E.subtract(temp);
List<Integer> zeroColumns = findZeroColumns(E);
E = removeZeroColumns(E, zeroColumns);
H = removeZeroColumns(H, zeroColumns);
Matrix JE = new Matrix(E.getData());
Matrix JH = new Matrix(H.getData());
if (JE.rank() < JE.getRowDimension()) {
Log.write(this, "Some error occurred (E matrix is singular)");
return -1;
} else {
double lambda;
if (useEigenvalues) {
Matrix L = JE.inverse().times(JH);
double[] eigs = L.eig().getRealEigenvalues();
Arrays.sort(eigs);
lambda = 1;
int nonNullEigs = n_y.keySet().size() - 1;
for (int i = eigs.length - nonNullEigs; i < eigs.length; i++) {
if (Math.abs(eigs[i]) < zeroThreshold) {
Log.write(this, "Some error occurred (E matrix has too many null eigenvalues)");
return -1;
}
lambda *= 1.0 / (1.0 + eigs[i]);
}
} else {
Matrix sum = JE.plus(JH);
if (sum.rank() < sum.getRowDimension()) {
Log.write(this, "Some error occourred (E+H is singular");
return -1;
}
lambda = JE.det() / sum.det();
}
return Math.sqrt(1 - lambda);
}
}