std::erf – cppreference.com

std::erf

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<tbody> </tbody>
definiert in Header <cmath>
float erf( float arg );
 (seit C++11)
double erf( double arg );
 (seit C++11)
long double erf( long double arg );
 (seit C++11)
double erf( Integral arg );
 (seit C++11)
Berechnet den Fehlerfunktion der arg .
Original:
Computes the Fehlerfunktion of arg.
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Parameter

arg -
Floating-Point-Wert
Original:
floating point value
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Rückgabewert

Der Wert der Fehlerfunktion der arg, das heißt
2
√π
∫arg
0e-t2
dt .
Original:
The value of the error function of arg, that is
2
√π
∫arg
0e-t2
dt.
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Beispiel

The following example calculates the probability that a normal variate is on the interval (x1, x2) 

#include <iostream>
#include <cmath>
#include <iomanip>
double phi(double x1, double x2)
{
    return (std::erf(x2/std::sqrt(2)) - std::erf(x1/std::sqrt(2)))/2;
}
int main()
{
    std::cout << "normal variate probabilities:\n";
    for(int n=-4; n<4; ++n)
        std::cout << "[" << std::setw(2) << n << ":" << std::setw(2) << n+1 << "]: "
                  << std::setw(5) << std::fixed << std::setprecision(2)
                  << 100*phi(n, n+1) << "%\n";
}

Output: 

normal variate probabilities:
[-4:-3]:  0.13%
[-3:-2]:  2.14%
[-2:-1]: 13.59%
[-1: 0]: 34.13%
[ 0: 1]: 34.13%
[ 1: 2]: 13.59%
[ 2: 3]:  2.14%
[ 3: 4]:  0.13%


Siehe auch

Externer Links

Weisstein, Eric W. "Erf." Von MathWorld - A Wolfram Web Resource .
Original:
Weisstein, Eric W. "Erf." From MathWorld--A Wolfram Web Resource.
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