erf_inverse

Evaluates the real inverse error function erf-1 (x).

Synopsis

#include <imsl.h>

float imsl_f_erf_inverse (float x)

The type double function is imsl_d_erf_inverse.

Required Arguments

float x (Input)
Point at which the inverse error function is to be evaluated. It must be between −1 and 1.

Return Value

The value of the inverse error function erf-1 (x).

Description

The inverse error function erf-1 (x) is such that x = erf (y), where

 

The inverse error function is defined only for −1 < x < 1.

 

Figure 1,  Plot of erf-1(x)

Example

Evaluate the inverse error function at x = 1/2.

 

#include <imsl.h>

#include <stdio.h>

 

int main()

{

float x = 0.5;

float ans;

 

ans = imsl_f_erfc_inverse(x);

printf("inverse erfc(%f) = %f\n", x, ans);

}

Output

 

inverse erf(0.500000) = 0.476936

Warning Errors

IMSL_LARGE_ABS_ARG_WARN

The answer is less accurate than half precision because |x| is too large.

Fatal Errors

IMSL_REAL_OUT_OF_RANGE

The inverse error function is defined only for −1 < x < 1.