/** * Compute a covariance matrix from a matrix whose columns represent * covariates. * @param matrix input matrix (must have at least one column and two rows) * @param biasCorrected determines whether or not covariance estimates are bias-corrected * @return covariance matrix * @throws MathIllegalArgumentException if the matrix does not contain sufficient data */ protected RealMatrix computeCovarianceMatrix(RealMatrix matrix, bool biasCorrected) { int dimension = matrix.getColumnDimension(); Variance variance = new Variance(biasCorrected); RealMatrix outMatrix = new BlockRealMatrix(dimension, dimension); for (int i = 0; i < dimension; i++) { for (int j = 0; j < i; j++) { double cov = covariance(matrix.getColumn(i), matrix.getColumn(j), biasCorrected); outMatrix.setEntry(i, j, cov); outMatrix.setEntry(j, i, cov); } outMatrix.setEntry(i, i, variance.evaluate(matrix.getColumn(i))); } return(outMatrix); }