erfcInv

Computes the inverse complementary error function at y.

Returns the value x such that erfc(x) = y. Equivalent to erfInv(1 - y) but accepts the complementary probability directly, which is convenient when working with tail probabilities. Used internally by quantile functions of distributions related to the normal distribution.

Example:

erfcInv(1.0)              // 0.0 (since erfc(0) = 1)
erfcInv(0.5) // 0.4769... (since erfc(0.4769) ≈ 0.5)
erfcInv(erfc(1.0)) // 1.0 (round-trip)

Return

the inverse complementary error function value at y.

Parameters

y

the value at which to evaluate. Must be strictly between 0 and 2 (exclusive).