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program example_exponential_cdf
use stdlib_random, only: random_seed
use stdlib_stats_distribution_exponential, only: exp_cdf => cdf_exp, &
rexp => rvs_exp
implicit none
real, dimension(2, 3, 4) :: x, loc, scale
real :: xsum
complex :: cloc, cscale
integer :: seed_put, seed_get, i
seed_put = 1234567
call random_seed(seed_put, seed_get)
! standard exponential cumulative distribution at x=1.0 with loc=0.0, scale=1.0
print *, exp_cdf(1.0, 0.0, 1.0)
! 0.632120550
! standard exponential cumulative distribution at x=1.0 with lambda=1.0
print *, exp_cdf(1.0, 1.0)
! 0.632120550
! cumulative distribution at x=2.0 with lambda=2
print *, exp_cdf(2.0, 2.0)
! 0.981684387
! cumulative distribution at x=2.0 with loc=0.0 and scale=0.5 (equivalent of lambda=2)
print *, exp_cdf(2.0, 0.0, 0.5)
! 0.981684387
! cumulative distribution at x=2.5 with loc=0.5 and scale=0.5 (equivalent of lambda=2)
print *, exp_cdf(2.5, 0.5, 0.5)
! 0.981684387
! cumulative distribution at x=2.0 with loc=0.0 and scale=-1.0 (out of range)
print *, exp_cdf(2.0, 0.0, -1.0)
! NaN
! cumulative distribution at x=0.5 with loc=1.0 and scale=1.0, putting x below the minimum
print *, exp_cdf(0.5, 1.0, 1.0)
! 0.00000000
! standard exponential random variates array
x = reshape(rexp(0.0, 2.0, 24), [2, 3, 4])
! a rank-3 exponential cumulative distribution
loc(:, :, :) = 0.0
scale(:, :, :) = 2.0
print *, exp_cdf(x, loc, scale)
! 0.301409245 0.335173965 5.94930053E-02 0.113003314
! 0.365694344 0.583515942 0.113774836 0.838585377
! 0.509324908 0.127967060 0.857194781 0.893231630
! 0.355383813 0.470882893 0.574203610 0.799321830
! 0.546216846 0.111995399 0.801794767 0.922525287
! 0.937719882 0.301136374 3.44503522E-02 0.134661376
! cumulative distribution array where scale<=0.0 for certain elements
print *, exp_cdf([1.0, 1.0, 1.0], [0.0, 0.0, 0.0], [1.0, 0.0, -1.0])
! 0.632120550 NaN NaN
! `cdf_exp` is pure and, thus, can be called concurrently
xsum = 0.0
do concurrent (i=1:size(x,3))
xsum = xsum + sum(exp_cdf(x(:,:,i), loc(:,:,i), scale(:,:,i)))
end do
print *, xsum
! 11.0886612
! complex exponential cumulative distribution at (0.5, 0.0, 2) with real part of
! scale=2 and imaginary part of scale=1.0
cloc = (0.0, 0.0)
cscale = (2, 1.0)
print *, exp_cdf((0.5, 0.5), cloc, cscale)
! 8.70351046E-02
! As above, but with scale%im < 0
cloc = (0.0, 0.0)
cscale = (1.0, -2.0)
print *, exp_cdf((1.5, 1.0), cloc, cscale)
! NaN
end program example_exponential_cdf
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