erfc, erfcf, erfcl
From cppreference.com
| Defined in header <math.h>
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| float erfcf( float arg ); |
(1) | (since C99) |
| double erfc( double arg ); |
(2) | (since C99) |
| long double erfcl( long double arg ); |
(3) | (since C99) |
| Defined in header <tgmath.h>
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| #define erfc( arg ) |
(4) | (since C99) |
1-3) Computes the complementary error function of
arg, that is 1.0-erf(arg), but without loss of precision for large arg.4) Type-generic macro: If
arg has type long double, erfcl is called. Otherwise, if arg has integer type or the type double, erfc is called. Otherwise, erfcf is called.Parameters
| arg | - | floating point value |
Return value
If no errors occur, value of the complementary error function ofarg, that is | 2 |
arge-t2
dt or 1-erf(arg), is returned.
If a range error occurs due to underflow, the correct result (after rounding) is returned.
Error handling
Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is +, +0 is returned
- If the argument is -, 2 is returned
- If the argument is NaN, NaN is returned
Notes
For the IEEE-compatible type double, underflow is guaranteed if arg > 26.55.
Example
Run this code
#include <stdio.h> #include <math.h> double normalCDF(double x) // Phi(-, x) aka N(x) { return erfc(-x/sqrt(2))/2; } int main(void) { puts("normal cumulative distribution function:"); for(double n=0; n<1; n+=0.1) printf("normalCDF(%.2f)%5.2f%%\n", n, 100*normalCDF(n)); puts("special values:"); printf("erfc(-Inf) =%f\n", erfc(-INFINITY)); printf("erfc(Inf) =%f\n", erfc(INFINITY)); }
Output:
normal cumulative distribution function: normalCDF(0.00) 50.00% normalCDF(0.10) 53.98% normalCDF(0.20) 57.93% normalCDF(0.30) 61.79% normalCDF(0.40) 65.54% normalCDF(0.50) 69.15% normalCDF(0.60) 72.57% normalCDF(0.70) 75.80% normalCDF(0.80) 78.81% normalCDF(0.90) 81.59% normalCDF(1.00) 84.13% special values: erfc(-Inf) = 2.000000 erfc(Inf) = 0.000000
References
- C11 standard (ISO/IEC 9899:2011):
- 7.12.8.2 The erfc functions (p: 249-250)
- 7.25 Type-generic math <tgmath.h> (p: 373-375)
- F.10.5.2 The erfc functions (p: 525)
- C99 standard (ISO/IEC 9899:1999):
- 7.12.8.2 The erfc functions (p: 230)
- 7.22 Type-generic math <tgmath.h> (p: 335-337)
- F.9.5.2 The erfc functions (p: 462)
See also
| (C99)(C99)(C99) |
computes error function (function) |