サブ　txp.js　　　Last modified: Mar 25, 2004

function txp(t, df)
{
  var m2pi, t1, t2, p, w, i
  m2pi = 0.636619772367581343076
  t1 = Math.abs(t)/Math.sqrt(df)
  t2 = 1.0/(1.0+t1*t1)
  if ((df%2) == 0) {
    for (w = t1*Math.sqrt(t2), p = 1.0-w, i = 2; i <= df-2; i += 2) {
      p -= w *= t2*(i-1)/i
    }
  }
  else {
    p = 1.0-m2pi*Math.atan(t1)
    if (df >= 3) {
      for (w = m2pi*t1*t2, p -= w, i = 3; i <= df-2; i += 2) {
        p -= w *= t2*(i-1)/i
      }
    }
  }
  return (p < 0.0 && Math.abs(p) < 1e-10) ? 0.0 : p
}