bessel.js

/* bessel.js (C) 2013-present SheetJS -- http://sheetjs.com */
/* vim: set ts=2: */
/*exported BESSEL */
var BESSEL;
(function (factory) {
  /*jshint ignore:start */
  if(typeof DO_NOT_EXPORT_BESSEL === 'undefined') {
    if('object' === typeof exports) {
      factory(exports);
    } else if ('function' === typeof define && define.amd) {
      define(function () {
        var module = {};
        factory(module);
        return module;
      });
    } else {
      factory(BESSEL = {});
    }
  } else {
    factory(BESSEL = {});
  }
  /*jshint ignore:end */
}(function(BESSEL) {
BESSEL.version = '1.0.2';
var M = Math;

function _horner(arr, v) { for(var i = 0, z = 0; i < arr.length; ++i) z = v * z + arr[i]; return z; }
function _bessel_iter(x, n, f0, f1, sign) {
  if(n === 0) return f0;
  if(n === 1) return f1;
  var tdx = 2 / x, f2 = f1;
  for(var o = 1; o < n; ++o) {
    f2 = f1 * o * tdx + sign * f0;
    f0 = f1; f1 = f2;
  }
  return f2;
}
function _bessel_wrap(bessel0, bessel1, name, nonzero, sign) {
  return function bessel(x,n) {
    if(nonzero) {
      if(x === 0) return (nonzero == 1 ? -Infinity : Infinity);
      else if(x < 0) return NaN;
    }
    if(n === 0) return bessel0(x);
    if(n === 1) return bessel1(x);
    if(n < 0) return NaN;
    n|=0;
    var b0 = bessel0(x), b1 = bessel1(x);
    return _bessel_iter(x, n, b0, b1, sign);
  };
}
var besselj = (function() {
  var W = 0.636619772; // 2 / Math.PI

  var b0_a1a = [57568490574.0, -13362590354.0, 651619640.7, -11214424.18, 77392.33017, -184.9052456].reverse();
  var b0_a2a = [57568490411.0, 1029532985.0, 9494680.718, 59272.64853, 267.8532712, 1.0].reverse();
  var b0_a1b = [1.0, -0.1098628627e-2, 0.2734510407e-4, -0.2073370639e-5, 0.2093887211e-6].reverse();
  var b0_a2b = [-0.1562499995e-1, 0.1430488765e-3, -0.6911147651e-5, 0.7621095161e-6, -0.934935152e-7].reverse();

  function bessel0(x) {
    var a=0, a1=0, a2=0, y = x * x;
    if(x < 8) {
      a1 = _horner(b0_a1a, y);
      a2 = _horner(b0_a2a, y);
      a = a1 / a2;
    } else {
      var xx = x - 0.785398164;
      y = 64 / y;
      a1 = _horner(b0_a1b, y);
      a2 = _horner(b0_a2b, y);
      a = M.sqrt(W/x)*(M.cos(xx)*a1-M.sin(xx)*a2*8/x);
    }
    return a;
  }

  var b1_a1a = [72362614232.0, -7895059235.0, 242396853.1, -2972611.439, 15704.48260, -30.16036606].reverse();
  var b1_a2a = [144725228442.0, 2300535178.0, 18583304.74, 99447.43394, 376.9991397, 1.0].reverse();
  var b1_a1b = [1.0, 0.183105e-2, -0.3516396496e-4, 0.2457520174e-5, -0.240337019e-6].reverse();
  var b1_a2b = [0.04687499995, -0.2002690873e-3, 0.8449199096e-5, -0.88228987e-6, 0.105787412e-6].reverse();

  function bessel1(x) {
    var a=0, a1=0, a2=0, y = x*x, xx = M.abs(x) - 2.356194491;
    if(Math.abs(x)< 8) {
      a1 = x*_horner(b1_a1a, y);
      a2 = _horner(b1_a2a, y);
      a = a1 / a2;
    } else {
      y = 64 / y;
      a1=_horner(b1_a1b, y);
      a2=_horner(b1_a2b, y);
      a=M.sqrt(W/M.abs(x))*(M.cos(xx)*a1-M.sin(xx)*a2*8/M.abs(x));
      if(x < 0) a = -a;
    }
    return a;
  }

  return function besselj(x, n) {
    n = Math.round(n);
    if(!isFinite(x)) return isNaN(x) ? x : 0;
    if(n < 0) return ((n%2)?-1:1)*besselj(x, -n);
    if(x < 0) return ((n%2)?-1:1)*besselj(-x, n);
    if(n === 0) return bessel0(x);
    if(n === 1) return bessel1(x);
    if(x === 0) return 0;

    var ret=0.0;
    if(x > n) {
      ret = _bessel_iter(x, n, bessel0(x), bessel1(x),-1);
    } else {
      var m=2*M.floor((n+M.floor(M.sqrt(40*n)))/2);
      var jsum=false;
      var bjp=0.0, sum=0.0;
      var bj=1.0, bjm = 0.0;
      var tox = 2 / x;
      for (var j=m;j>0;j--) {
        bjm=j*tox*bj-bjp;
        bjp=bj;
        bj=bjm;
        if (M.abs(bj) > 1E10) {
          bj *= 1E-10;
          bjp *= 1E-10;
          ret *= 1E-10;
          sum *= 1E-10;
        }
        if (jsum) sum += bj;
        jsum=!jsum;
        if (j == n) ret=bjp;
      }
      sum=2.0*sum-bj;
      ret /= sum;
    }
    return ret;
  };
})();
var bessely = (function() {
  var W = 0.636619772;

  var b0_a1a = [-2957821389.0, 7062834065.0, -512359803.6, 10879881.29, -86327.92757, 228.4622733].reverse();
  var b0_a2a = [40076544269.0, 745249964.8, 7189466.438, 47447.26470, 226.1030244, 1.0].reverse();
  var b0_a1b = [1.0, -0.1098628627e-2, 0.2734510407e-4, -0.2073370639e-5, 0.2093887211e-6].reverse();
  var b0_a2b = [-0.1562499995e-1, 0.1430488765e-3, -0.6911147651e-5, 0.7621095161e-6, -0.934945152e-7].reverse();

  function bessel0(x) {
    var a=0, a1=0, a2=0, y = x * x, xx = x - 0.785398164;
    if(x < 8) {
      a1 = _horner(b0_a1a, y);
      a2 = _horner(b0_a2a, y);
      a = a1/a2 + W * besselj(x,0) * M.log(x);
    } else {
      y = 64 / y;
      a1 = _horner(b0_a1b, y);
      a2 = _horner(b0_a2b, y);
      a = M.sqrt(W/x)*(M.sin(xx)*a1+M.cos(xx)*a2*8/x);
    }
    return a;
  }

  var b1_a1a = [-0.4900604943e13, 0.1275274390e13, -0.5153438139e11, 0.7349264551e9, -0.4237922726e7, 0.8511937935e4].reverse();
  var b1_a2a = [0.2499580570e14, 0.4244419664e12, 0.3733650367e10, 0.2245904002e8, 0.1020426050e6, 0.3549632885e3, 1].reverse();
  var b1_a1b = [1.0, 0.183105e-2, -0.3516396496e-4, 0.2457520174e-5, -0.240337019e-6].reverse();
  var b1_a2b = [0.04687499995, -0.2002690873e-3, 0.8449199096e-5, -0.88228987e-6, 0.105787412e-6].reverse();

  function bessel1(x) {
    var a=0, a1=0, a2=0, y = x*x, xx = x - 2.356194491;
    if(x < 8) {
      a1 = x*_horner(b1_a1a, y);
      a2 = _horner(b1_a2a, y);
      a = a1/a2 + W * (besselj(x,1) * M.log(x) - 1 / x);
    } else {
      y = 64 / y;
      a1=_horner(b1_a1b, y);
      a2=_horner(b1_a2b, y);
      a=M.sqrt(W/x)*(M.sin(xx)*a1+M.cos(xx)*a2*8/x);
    }
    return a;
  }

  return _bessel_wrap(bessel0, bessel1, 'BESSELY', 1, -1);
})();
var besseli = (function() {
  var b0_a = [1.0, 3.5156229, 3.0899424, 1.2067492, 0.2659732, 0.360768e-1, 0.45813e-2].reverse();
  var b0_b = [0.39894228, 0.1328592e-1, 0.225319e-2, -0.157565e-2, 0.916281e-2, -0.2057706e-1, 0.2635537e-1, -0.1647633e-1, 0.392377e-2].reverse();

  function bessel0(x) {
    if(x <= 3.75) return _horner(b0_a, x*x/(3.75*3.75));
    return M.exp(M.abs(x))/M.sqrt(M.abs(x))*_horner(b0_b, 3.75/M.abs(x));
  }

  var b1_a = [0.5, 0.87890594, 0.51498869, 0.15084934, 0.2658733e-1, 0.301532e-2, 0.32411e-3].reverse();
  var b1_b = [0.39894228, -0.3988024e-1, -0.362018e-2, 0.163801e-2, -0.1031555e-1, 0.2282967e-1, -0.2895312e-1, 0.1787654e-1, -0.420059e-2].reverse();

  function bessel1(x) {
    if(x < 3.75) return x * _horner(b1_a, x*x/(3.75*3.75));
    return (x < 0 ? -1 : 1) * M.exp(M.abs(x))/M.sqrt(M.abs(x))*_horner(b1_b, 3.75/M.abs(x));
  }

  return function besseli(x, n) {
    n = Math.round(n);
    if(n === 0) return bessel0(x);
    if(n === 1) return bessel1(x);
    if(n < 0) return NaN;
    if(M.abs(x) === 0) return 0;
    if(x == Infinity) return Infinity;

    var ret = 0.0, j, tox = 2 / M.abs(x), bip = 0.0, bi=1.0, bim=0.0;
    var m=2*M.round((n+M.round(M.sqrt(40*n)))/2);
    for (j=m;j>0;j--) {
      bim=j*tox*bi + bip;
      bip=bi; bi=bim;
      if (M.abs(bi) > 1E10) {
        bi *= 1E-10;
        bip *= 1E-10;
        ret *= 1E-10;
      }
      if(j == n) ret = bip;
    }
    ret *= besseli(x, 0) / bi;
    return x < 0 && (n%2) ? -ret : ret;
  };

})();

var besselk = (function() {
  var b0_a = [-0.57721566, 0.42278420, 0.23069756, 0.3488590e-1, 0.262698e-2, 0.10750e-3, 0.74e-5].reverse();
  var b0_b = [1.25331414, -0.7832358e-1, 0.2189568e-1, -0.1062446e-1, 0.587872e-2, -0.251540e-2, 0.53208e-3].reverse();

  function bessel0(x) {
    if(x <= 2) return -M.log(x/2) * besseli(x,0) + _horner(b0_a, x*x/4);
    return M.exp(-x) / M.sqrt(x) * _horner(b0_b, 2/x);
  }

  var b1_a = [1.0, 0.15443144, -0.67278579, -0.18156897, -0.1919402e-1, -0.110404e-2, -0.4686e-4].reverse();
  var b1_b = [1.25331414, 0.23498619, -0.3655620e-1, 0.1504268e-1, -0.780353e-2, 0.325614e-2, -0.68245e-3].reverse();

  function bessel1(x) {
    if(x <= 2) return M.log(x/2) * besseli(x,1) + (1/x) * _horner(b1_a, x*x/4);
    return M.exp(-x)/M.sqrt(x)*_horner(b1_b, 2/x);
  }

  return _bessel_wrap(bessel0, bessel1, 'BESSELK', 2, 1);
})();
BESSEL.besselj = besselj;
BESSEL.bessely = bessely;
BESSEL.besseli = besseli;
BESSEL.besselk = besselk;
}));