[Scilab-users] Computing with very large numbers in Scilab

[Pinçon Bruno]

Le 01/01/2015 17:08, Rafael Guerra a écrit :
> Dear Scilab'ers,
>
> Happy New Year.
> Does someone know to perform in Scilab computations involving very large
> numbers?
> For example, the how to compute the following probability formula:
> 1-365!/((365-23)! *365^23)
>
> 1-factorial(365)/(factorial(365-23)* 365^23)   produces Nan in Scilab
> The correct answer (using Wolfram Alpha) is: 0.507...
>

    You should work around the formula such that too large numbers are 
avoided.
   In your case it is easy :

       365!/((365-23)! *365^23) = 
((365-22)*(365-21)*.......*(365-0))/(365 * 365 * ..... * 365)
         =  (343/365)*(344/365)*....*(364/365)*(365/365)

  In scilab this can be coded this way :

    1 - prod( (343:364)/365 )

  hth
B.