How to generate a certain number of random numbers from a gamma distribution that sum to a specific number

Question

John 2012-6-21

Hello,

Would anybody know how to generate a specific number of random numbers from a Gamma Distribution that sum to a particular value?

I have (1) the total distance that one travels in a day and (2) the number of journey that they make.

For example:

Total Distance = 40 miles No. Journeys = 3

I'm trying to generate 3 random numbers from a Gamma distribution that sum to 40.

Appreciate any help with this

Thank you

JOhn

Answer 1

Walter Roberson 2012-6-21

You could try adapting http://www.mathworks.com/matlabcentral/fileexchange/9700 but the infinite tail might give some problems.

The result might not have the same gamma distribution as you started with.