# ErfInv

Computes inverse error function value of vector elements.

## Syntax

Fortran:

call vserfinv( n, a, y )

call vderfinv( n, a, y )

C:

vsErfInv( n, a, y );

vdErfInv( n, a, y );

## Input Parameters

Name | Type | Description
--- | --- | ---
n | FORTRAN: INTEGER, INTENT(IN) C: int | Specifies the number of elements to be calculated.
a | FORTRAN: REAL, INTENT(IN) for vserfinv DOUBLE PRECISION, INTENT(IN) for vderfinv C: const float* for vsErfInv const double* for vdErfInv | FORTRAN: Array, specifies the input vector a. C: Pointer to an array that contains the input vector a.

## Output Parameters

Name | Type | Description
--- | --- | ---
y | FORTRAN: REAL for vserfinv DOUBLE PRECISION for vderfinv C: float* for vsErfInv double* for vdErfInv | FORTRAN: Array, specifies the output vector y. C: Pointer to an array that contains the output vector y.

## Description

The function ErfInv computes the inverse error function values for elements of the input vector a and writes them to the output vector y

`y = erf-1(a)`,

where `erf(x)` is the error function defined as given by:

Useful relations:

where erfc is the complementary error function.

where

is the cumulative normal distribution function.

where `Φ-1(x)` and `erf-1(x)` are the inverses to `Φ(x)` and `erf(x)` respectively.

Parent topic: Special Functions