calcBasisFunctionDerivatives function

dynamic calcBasisFunctionDerivatives(dynamic span, dynamic u, dynamic p, dynamic n, dynamic U,)

Implementation

calcBasisFunctionDerivatives(span, u, p, n, U) {
  var zeroArr = [];
  for (var i = 0; i <= p; ++i) {
    zeroArr[i] = 0.0;
  }

  var ders = [];

  for (var i = 0; i <= n; ++i) {
    ders[i] = zeroArr.sublist(0);
  }

  var ndu = [];

  for (var i = 0; i <= p; ++i) {
    ndu[i] = zeroArr.sublist(0);
  }

  ndu[0][0] = 1.0;

  var left = zeroArr.sublist(0);
  var right = zeroArr.sublist(0);

  for (var j = 1; j <= p; ++j) {
    left[j] = u - U[span + 1 - j];
    right[j] = U[span + j] - u;

    var saved = 0.0;

    for (var r = 0; r < j; ++r) {
      var rv = right[r + 1];
      var lv = left[j - r];
      ndu[j][r] = rv + lv;

      var temp = ndu[r][j - 1] / ndu[j][r];
      ndu[r][j] = saved + rv * temp;
      saved = lv * temp;
    }

    ndu[j][j] = saved;
  }

  for (var j = 0; j <= p; ++j) {
    ders[0][j] = ndu[j][p];
  }

  for (var r = 0; r <= p; ++r) {
    var s1 = 0;
    var s2 = 1;

    var a = [];
    for (var i = 0; i <= p; ++i) {
      a[i] = zeroArr.sublist(0);
    }

    a[0][0] = 1.0;

    for (var k = 1; k <= n; ++k) {
      var d = 0.0;
      var rk = r - k;
      var pk = p - k;

      if (r >= k) {
        a[s2][0] = a[s1][0] / ndu[pk + 1][rk];
        d = a[s2][0] * ndu[rk][pk];
      }

      var j1 = (rk >= -1) ? 1 : -rk;
      var j2 = (r - 1 <= pk) ? k - 1 : p - r;

      for (var j = j1; j <= j2; ++j) {
        a[s2][j] = (a[s1][j] - a[s1][j - 1]) / ndu[pk + 1][rk + j];
        d += a[s2][j] * ndu[rk + j][pk];
      }

      if (r <= pk) {
        a[s2][k] = -a[s1][k - 1] / ndu[pk + 1][r];
        d += a[s2][k] * ndu[r][pk];
      }

      ders[k][r] = d;

      var j = s1;
      s1 = s2;
      s2 = j;
    }
  }

  var r = p;

  for (var k = 1; k <= n; ++k) {
    for (var j = 0; j <= p; ++j) {
      ders[k][j] *= r;
    }

    r *= p - k;
  }

  return ders;
}