Random generating of parameters

[vanair]

Dear all,

i am beginner in AMPL and so need your help!!
I need to generate integer parameters with a discrete uniform distribution.
Should i use build in function Uniform(m,n) and then round the values? or
there is also different solution?

I will highly appreciate your advice and help!

Greetings

Anna
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[Paul]

On Oct 28, 12:48 pm, vanair <a.varshav...@gmail.com> wrote:

> I need to generate  integer parameters with a discrete uniform distribution.
> Should i use build in function Uniform(m,n) and then round the values? or
> there is also different solution?

Rounding Uniform(1,5) will give you a result that takes values 2, 3, 4
with probability .25 each and 1 and 5 with probability .125 each
(because you cannot hit 5 rounding down or 1 rounding up). If you
want U{1,...,5}, generate a value from Uniform(1,6) and then truncate
it (use the trunc function).

/Paul

[vanair]

Thanks a lot for advise!!!!!!!!!!!!
can i ask you another question.
I am randomly generating integer values for a parameter b[i,t] for each time
period t and everything goes well:

param b{i in I, t in T} = Uniform(1,5);

But how can i generate a value in different range for each parameter b[i,t]
separately. For example:
b[1,t] = Uniform(1,5);
b[2,t] = Uniform(10,20);

Is there any solution?
thanks a lot in advance!!!!!

Anna

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[Paul]

On Oct 29, 9:38 am, vanair <a.varshav...@gmail.com> wrote:

> I am randomly generating integer values for a parameter b[i,t] for each time
> period t and everything goes well:
>
> param b{i in I, t in T} = Uniform(1,5);
>
> But how can i generate a value in different range for each parameter b[i,t]
> separately. For example:
> b[1,t] = Uniform(1,5);
> b[2,t] = Uniform(10,20);
>

One approach: Make the arguments of the Uniform function expressions
in i and t. For instance,

param b {i in I, t in T} := Uniform((i-1)*t, i*t);

Another approach: Read the arguments of the Uniform function from a
data file. Something like

param blo {I, T}; # lower limits of distribution, read from data file
param bhi {I, T}; # upper limits of distribution, read from data file
param b {i in I, t in T} default Uniform(blo[i, t], bhi[i,t]);

/Paul

[vanair]

Thank you so much for help, Paul!!!

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[khan]

Greetings,

Is there any way to use Uniform function to generate numbers in a single row and multiple columns?

Thanx.

[AMPL Google Group]

You can two params to define the range for Uniform() function and generate the random value for each pair of low and high.
Here is an example:
param n :=2;
param low{1..n};
param high{1..n};
param d{i in 1..n} := Uniform(low[i],high[i]);
data;
param low := 1 0 2 0;
param high := 1 1 2 1;

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