private void cal(double[] cum, double factor, int d, int n, int p1, double[] res) { if (n == 1) { return; } int n1 = n / 2; int n2 = n - n1; double s = (cum[p1 + n1] - cum[p1]) * factor; double c = 1 - s; res[d] = s; cal(cum, factor / s, d + 1, n1, p1, res); cal(cum, factor / c, d + n1, n2, p1 + n1, res); }
/** * Inverse transform from the N "model" parameters to the N-1 "fit" parameters. * Used mainly to find the start position of a optimisation routine. * * @param modelParms The N "model" parameters. <b>These must sum to one</b> * @return The N-1 "fit" parameters */ public double[] inverseTransform(double[] modelParms) { ArgChecker.isTrue(modelParms.length == _n, "length of modelParms is {}, but must be {} ", modelParms.length, _n); double[] res = new double[_n - 1]; double[] cum = new double[_n + 1]; double sum = 0.0; for (int i = 0; i < _n; i++) { sum += modelParms[i]; cum[i + 1] = sum; } ArgChecker.isTrue(Math.abs(sum - 1.0) < TOL, "sum of elements is {}. Must be 1.0", sum); cal(cum, 1.0, 0, _n, 0, res); for (int i = 0; i < _n - 1; i++) { res[i] = Math.asin(Math.sqrt(res[i])); } return res; }