Evaluates the real inverse error function erf-1 (x).
Synopsis
#include <imsl.h>
float imsl_f_erf_inverse (float x)
The type double procedure 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 9- 3 Plot of erf -1 (x)
Example
Evaluate the inverse error function at x = 1/2.
#include
<imsl.h>
main()
{
float x = 0.5;
float ans;
ans =
imsl_f_erf_inverse(x);
printf("inverse erf(%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.
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