api/html/agrad_2rev_2functions_2_phi__approx_8hpp_source.html

 #ifndef STAN__AGRAD__REV__FUNCTIONS__PHI_APPROX_HPP

 #define STAN__AGRAD__REV__FUNCTIONS__PHI_APPROX_HPP


 #include <stan/agrad/rev/var.hpp>

 #include <stan/agrad/rev/internal/precomp_v_vari.hpp>

 #include <stan/math/functions/inv_logit.hpp>


 namespace stan {

   namespace agrad {


     inline var Phi_approx(const stan::agrad::var& a) {

       // return inv_logit(0.07056 * pow(a,3.0) + 1.5976 * a);


       double av = a.vi_->val_;

       double av_squared = av * av;

       double av_cubed = av * av_squared;

       double f = stan::math::inv_logit(0.07056 * av_cubed + 1.5976 * av);

       double da = f * (1 - f) * (3.0 * 0.07056 * av_squared + 1.5976);

       return var(new precomp_v_vari(f,a.vi_,da));

     }


   }

 }

 #endif

precomp_v_vari.hpp

stan::agrad::Phi_approx
var Phi_approx(const stan::agrad::var &a)
Approximation of the unit normal CDF for variables (stan).
Definition: Phi_approx.hpp:48

stan::agrad::vari::val_
const double val_
The value of this variable.
Definition: vari.hpp:37

stan::math::inv_logit
boost::math::tools::promote_args< T >::type inv_logit(const T a)
Returns the inverse logit function applied to the argument.
Definition: inv_logit.hpp:52

stan::agrad::var::vi_
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:40

var.hpp

stan::agrad::precomp_v_vari
Definition: precomp_v_vari.hpp:11

stan::agrad::var
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:27

inv_logit.hpp