Thread Subject:

inverse gamma function

i like to solve the equation given bellow-
  f=incomplete gamma function(u,x);
f=.0001;
u=5;
now ilike to find out x.

i have tried like-
 x=gammaincinv((1-f),u,'lower')

On 7 Jul., 11:35, "Dipen Bepari" <dipen.jge...@gmail.com> wrote:
> i like to solve the equation given bellow-
>   f=incomplete gamma function(u,x);
> f=.0001;
> u=5;
> now ilike to find out x.
>
> i have tried like-
>  x=gammaincinv((1-f),u,'lower')

You can easily check whether you are right by
calculating hereafter
y=gammainc(x,u)
If y=f, you are done (assuming you use the same definition for the
gammainc function as MATLAB does).

Best wishes
Torsten.

"Dipen Bepari" <dipen.jgec04@gmail.com> wrote in message <iv3ukf$and$1@newscl01ah.mathworks.com>...
> i like to solve the equation given bellow-
> f=incomplete gamma function(u,x);
> f=.0001;
> u=5;
> now ilike to find out x.
>
> i have tried like-
> x=gammaincinv((1-f),u,'lower')
- - - - - - - - - - - -
  You are attempting to find the inverse with respect to the second argument - the gamma function parameter - of gammainc. However, the function gammaincinv finds the inverse with respect to the first argument - the limit of integration - which is a very different problem.

  Why don't you try using fzero on it?

Roger Stafford