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List of integrals of Gaussian functions

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In these expressions

Contents

ϕ ( x ) = 1 2 π e 1 2 x 2

is the standard normal probability density function,

Φ ( x ) = x ϕ ( t ) d t = 1 2 ( 1 + erf ( x 2 ) )

is the corresponding cumulative distribution function (where erf is the error function) and

T ( h , a ) = ϕ ( h ) 0 a ϕ ( h x ) 1 + x 2 d x

is known as the Owen's T function.

Owen has an extensive list of Gaussian-type integrals; only a subset is given below.

Indefinite integrals

ϕ ( x ) d x = Φ ( x ) + C x ϕ ( x ) d x = ϕ ( x ) + C x 2 ϕ ( x ) d x = Φ ( x ) x ϕ ( x ) + C x 2 k + 1 ϕ ( x ) d x = ϕ ( x ) j = 0 k ( 2 k ) ! ! ( 2 j ) ! ! x 2 j + C x 2 k + 2 ϕ ( x ) d x = ϕ ( x ) j = 0 k ( 2 k + 1 ) ! ! ( 2 j + 1 ) ! ! x 2 j + 1 + ( 2 k + 1 ) ! ! Φ ( x ) + C

In these integrals, n!! is the double factorial: for even n it is equal to the product of all even numbers from 2 to n, and for odd n it is the product of all odd numbers from 1 to n, additionally it is assumed that 0!! = (−1)!! = 1.

ϕ ( x ) 2 d x = 1 2 π Φ ( x 2 ) + C ϕ ( x ) ϕ ( a + b x ) d x = 1 t ϕ ( a t ) Φ ( t x + a b t ) + C , t = 1 + b 2 x ϕ ( a + b x ) d x = 1 b 2 ( ϕ ( a + b x ) + a Φ ( a + b x ) ) + C x 2 ϕ ( a + b x ) d x = 1 b 3 ( ( a 2 + 1 ) Φ ( a + b x ) + ( a b x ) ϕ ( a + b x ) ) + C ϕ ( a + b x ) n d x = 1 b n ( 2 π ) n 1 Φ ( n ( a + b x ) ) + C Φ ( a + b x ) d x = 1 b ( ( a + b x ) Φ ( a + b x ) + ϕ ( a + b x ) ) + C x Φ ( a + b x ) d x = 1 2 b 2 ( ( b 2 x 2 a 2 1 ) Φ ( a + b x ) + ( b x a ) ϕ ( a + b x ) ) + C x 2 Φ ( a + b x ) d x = 1 3 b 3 ( ( b 3 x 3 + a 3 + 3 a ) Φ ( a + b x ) + ( b 2 x 2 a b x + a 2 + 2 ) ϕ ( a + b x ) ) + C x n Φ ( x ) d x = 1 n + 1 ( ( x n + 1 n x n 1 ) Φ ( x ) + x n ϕ ( x ) + n ( n 1 ) x n 2 Φ ( x ) d x ) + C x ϕ ( x ) Φ ( a + b x ) d x = b t ϕ ( a t ) Φ ( x t + a b t ) ϕ ( x ) Φ ( a + b x ) + C , t = 1 + b 2 Φ ( x ) 2 d x = x Φ ( x ) 2 + 2 Φ ( x ) ϕ ( x ) 1 π Φ ( x 2 ) + C e c x ϕ ( b x ) n d x = e c 2 2 n b 2 b n ( 2 π ) n 1 Φ ( b 2 x n c b n ) + C , b 0 , n > 0

Definite integrals

x 2 ϕ ( x ) n d x = 1 n 3 ( 2 π ) n 1 0 ϕ ( a x ) Φ ( b x ) d x = 1 2 π | a | ( π 2 arctan ( b | a | ) ) 0 ϕ ( a x ) Φ ( b x ) d x = 1 2 π | a | ( π 2 + arctan ( b | a | ) ) 0 x ϕ ( x ) Φ ( b x ) d x = 1 2 2 π ( 1 + b 1 + b 2 ) 0 x 2 ϕ ( x ) Φ ( b x ) d x = 1 4 + 1 2 π ( b 1 + b 2 + arctan ( b ) ) 0 x ϕ ( x ) 2 Φ ( x ) d x = 1 4 π 3 0 Φ ( b x ) 2 ϕ ( x ) d x = 1 2 π ( arctan ( b ) + arctan 1 + 2 b 2 ) Φ ( a + b x ) 2 ϕ ( x ) d x = Φ ( a 1 + b 2 ) 2 T ( a 1 + b 2 , 1 1 + 2 b 2 ) x Φ ( a + b x ) 2 ϕ ( x ) d x = 2 b 1 + b 2 ϕ ( a t ) Φ ( a 1 + b 2 1 + 2 b 2 ) Φ ( b x ) 2 ϕ ( x ) d x = 1 π arctan 1 + 2 b 2 x ϕ ( x ) Φ ( b x ) d x = x ϕ ( x ) Φ ( b x ) 2 d x = b 2 π ( 1 + b 2 ) Φ ( a + b x ) ϕ ( x ) d x = Φ ( a 1 + b 2 ) x Φ ( a + b x ) ϕ ( x ) d x = b t ϕ ( a t ) , t = 1 + b 2 0 x Φ ( a + b x ) ϕ ( x ) d x = b t ϕ ( a t ) Φ ( a b t ) + 1 2 π Φ ( a ) , t = 1 + b 2 ln ( x 2 ) 1 σ ϕ ( x σ ) d x = ln ( σ 2 ) γ ln 2 ln ( σ 2 ) 1.27036

References

List of integrals of Gaussian functions Wikipedia


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