Excel Poisson function in FileMaker

Question asked by FrankPottner on Jul 3, 2017
Latest reply on Jul 5, 2017 by fmpdude

I'm looking for some ideas on how to create the equivalent of the cumulative distribution Excel Poisson function in FileMaker.

The function takes 2 parameters; X and Lambda and is described here;

https://wiki.openoffice.org/wiki/Documentation/How_Tos/Calc:_POISSON_function

It evaluates to the sum of the following formula from 0 to X;

Exp(-1 * Lambda)  *   (Lamda ^ X)    /     Factorial(X)

The problem is when Lambda is greater than 37 the formula returns 0 due to the first part ie

Exp(-37) = 1.0e-16

Exp(-38) = 0

and Factorial(X) returns "?" with values higher than 212.

I was hoping to find a Javascript equivalent of this function.

My plan was to;

- in a global field create a HTML/Javascript page that evaluates the function

- use FileMaker's WebViewer to read the page & result

I haven't had any luck finding a Javascript equivalent to the Excel function.

I did find some sample code with the limits on Lambda at around 100 which is better but not great.

The result of the Poisson function needs to be update immediately as X or Lambda is changed, and the solution needs to be WebDirect compliant.

Does anyone have any suggestions?