Rounded random numbers with fixed sum

18 visualizaciones (últimos 30 días)
Thomas Coppin
Thomas Coppin el 10 de Ag. de 2020
Comentada: Thomas Coppin el 10 de Ag. de 2020
I'm trying to generate a 1xK array with 'random' numbers that sum to 1, but that are also rounded to either 1 or 2 decimal places.
For example, if K=3, and I want the numbers to 2 decimal places, this is what I would expect:
array = [0.27, 0.45, 0.27].
So far I am unable to achieve this. Here is my code.
K = 3;
r = rand(1,K);
r = round(r/sum(r),2);
Without rounding the numbers sum to 1, but once rounded the numbers only to sum to 1 approximately 50% of the time.
Any help would be greatly appreciated, thanks!
  2 comentarios
madhan ravi
madhan ravi el 10 de Ag. de 2020
sum(array) is not exactly one?
Thomas Coppin
Thomas Coppin el 10 de Ag. de 2020
No, once you round the values (after dividing by the sum) they no longer sum to exactly one.

Iniciar sesión para comentar.

Respuestas (2)

Walter Roberson
Walter Roberson el 10 de Ag. de 2020
Editada: Walter Roberson el 10 de Ag. de 2020
Multiply your desired total by 10 to the number of digits you need. Generate using Roger's code. Divide everything by 10 to the number of digits you need.
The sum of these will not in general be exactly the required value due to round off when adding floating-point numbers. In the test I just did of 1000 integers from 1 to 999, sum(v) /10 was different than sum(v/10) by 2*eps() of the value.

Bruno Luong
Bruno Luong el 10 de Ag. de 2020
k = 3;
r = (diff([0 sort(randperm(100+k-1,k-1)) 100+k])-1)/100
  4 comentarios
Bruno Luong
Bruno Luong el 10 de Ag. de 2020
Editada: Bruno Luong el 10 de Ag. de 2020
No but you can use Roger's RANDFIXEDSUM
k = 3;
x = round([0; cumsum(randfixedsum(k, 1, 100, 0, 0.5*100))]);
x(end) = 100; % prevent floating point error
r = diff(x')/100
The distribution might be not perfectly uniform but possibly close enough and suitable for what ever you want to do with it.
Thomas Coppin
Thomas Coppin el 10 de Ag. de 2020
Thanks Bruno, that does exactly what I require.

Iniciar sesión para comentar.

Categorías

Más información sobre Random Number Generation en Help Center y File Exchange.

Productos


Versión

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by