# How do I sample randomly based on some probability(wightage)?

Tue May 26 20:58:02 CEST 2009

```Sumitava Mukherjee <smukh at cognobytes.com> writes:

> On May 26, 11:39 pm, Sumitava Mukherjee <sm... at cognobytes.com> wrote:
>> Hi all,
>> I need to randomly sample from a list where all choices have weights
>> attached to them. The probability of them being choosen is dependent
>> on the weights.
>> If say Sample list of choices are [A,B,C,D,E] and weights of the same
>> are [0.895,0.567,0.765,0.890,0.60] when I draw (say 2) samples then I
>> want the likeliness of them being chosen be in the order : D>A>C>E>B

You mean A > D > C > E > B

>> In short I mean if prob of a H is .9 and probability of T be 0.1 then
>> if I draw 10 samples, 9 should be H and 1 should be T.
>>
>> I coudn't find a function in the module random that does so.
>> Please can someone guide me how the above could be implemented [either
>> through some function which exists and I don't know or pointers to
>> some code snippets which does so]?
>
>>>>> [Oh, I forgot to mention. I am looking for sampling without replacement.]

If you do sampling without replacement, you need to know the exact
number of each of A, B, C, D, E in the sample, not just their relative
frequency.

--
Arnaud

```