first commit

utils/math.js

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+// 标准正态分布误差函数
+function erf(x) {
+  // 使用近似公式计算误差函数
+  const a1 =  0.254829592;
+  const a2 = -0.284496736;
+  const a3 =  1.421413741;
+  const a4 = -1.453152027;
+  const a5 =  1.061405429;
+  const p  =  0.3275911;
+
+  const sign = (x >= 0) ? 1 : -1;
+  x = Math.abs(x);
+
+  const t = 1.0 / (1.0 + p * x);
+  const y = 1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * Math.exp(-x * x);
+
+  return sign * y;
+}
+
+module.exports = {
+  erf
+};