Fortran 生成正态分布数据
本例提供了用Fortran生成正态分布数据的代码和示范。完全符合Fortran语法，可直接使用。本例使用了 Fortran90 提供的 random_seed 和 random_number 函数，用户无需手动再调用他们。
Module ran_mod
Implicit None
! ran return a uniform random number between 0-1
! norma return a normal distribution
contains
function ran() !returns random number between 0 - 1
implicit none
integer , save :: flag = 0
double precision :: ran
if(flag==0) then
call random_seed()
flag = 1
endif
call random_number(ran) ! built in fortran 90 random number function
end function ran
function normal(mean,sigma)
implicit none
integer :: flag
double precision, parameter :: pi = 3.141592653589793239
double precision :: u1, u2, y1, y2, normal, mean, sigma
save flag
data flag /0/
u1 = ran(); u2 = ran()
if (flag.eq.0) then
y1 = sqrt(-2.0d0*log(u1))*cos(2.0d0*pi*u2)
normal = mean + sigma*y1
flag = 1
else
y2 = sqrt(-2.0d0*log(u1))*sin(2.0d0*pi*u2)
normal = mean + sigma*y2
flag = 0
endif
end function normal
!The above codes are made in Fortran 90 language, if you have any question, you may write to sealin2008@hotmail.com
End Module ran_mod
Program www_fcode_cn
use ran_mod
Implicit None
Integer , parameter :: N = 10000
Real( Kind = 8 ) :: a( N )
integer :: i
Open( 12 , File = 'out.txt' )
Do i = 1 , N
a( i ) = normal( 5.0D0 , 2.0D0 )
write( 12 , * ) a(i)
End Do
Close( 12 )
End Program www_fcode_cn
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