[R] generate random numbers for lotteries

[Vale Fara]

Hi,

thank you both for your replies, I really appreciate it!

To Mike: yes, random integers. Can I use the function round() as in
the example with 5 random numbers below?

To Billy: for the second part I got an error, but it may be that I
didn't properly set "i"...?
Here is the R output:
x <- runif(60 , 0 , 10) # 60 numbers from 0 to 10
> x
 [1] 3.29208009 8.62643979 3.40762875 0.35224714 6.78760173 4.72160818 etc
y<-  runif(60, 15 , 25) # same as above , from 15 to 25
> y
 [1] 18.48391 24.44361 23.20955 16.61257 23.06074 17.71158 23.67585 19.31675 etc
i <- 12
> i
[1] 12
> for( i in 1:length(x)) {
+ z = x[i] + y[i]
+ return z}
Errore: unexpected symbol in:
"z = x[i] + y[i]
return z"

To all: I attach an example with only 5 random numbers

step 1. random number generation
x <- round(runif(5 , 0 , 10) )
< x
 [1]  2 1  0  6  8
y <- round(runif(5 , 15 , 25) )
> y
 [1] 21 24 22 22 19

step2. matching of numbers from x and y to create lotteries
lottery 1: 2$ with 50% probability vs.  21$ with 50% of probability
(Expected value: 2*0.5+21*0.5=11.5)
lottery 2: 1$ with 50% probability vs.  24$ with 50% of probability
(Expected value: 1*0.5+24*0.5=12.5)
lottery 3: 0$ with 50% probability vs.  22$ with 50% of probability
(Expected value: 0*0.5+22*0.5=11)
lottery 4: 6$ with 50% probability vs.  22$ with 50% of probability
(Expected value: 6*0.5+22*0.5=14)
lottery 5: 8$ with 50% probability vs.  19$ with 50% of probability
(Expected value: 8*0.5+19*0.5=13.5)

step 3. Form step 2, I know that the min EV of these lotteries is 11
and the max EV is 14.
The difference is: max EV - min EV = 3.
I need a difference of 5

How to do this?

Valeria



2012/4/29 billy am <wickedpuppy at gmail.com>:
> Interesting set of question.. I am completely new to R but let me try my
> luck.
>
> Random number in R
>
> x <- runif(60 , 0 , 10) # 60 numbers from 0 to 10
> y<-  runif(60, 15 , 25) # same as above , from 15 to 25
>
> The second part though. Do you mean ,
>
> for( i in 1:length(x)) {
> z = x[i] + y[i]
> return z
> }
>
> something like that? No idea about the third part though.
>
> regards
> Billy
>
> On Sun, Apr 29, 2012 at 9:29 AM, Mike Miller <mbmiller+l at gmail.com> wrote:
>>
>> On Fri, 27 Apr 2012, Vale Fara wrote:
>>
>>> I am working with lotteries and I need to generate two sets of uniform
>>> random numbers.
>>>
>>> Requirements:
>>> 1) each set has 60 random numbers
>>
>>
>> random integers?
>>
>>
>>> 2) random numbers in the first set are taken from an interval (0-10),
>>> whereas numbers in the second set are taken from a higher interval
>>> (15-25)
>>
>>
>> Depends on if you mean integers.  R has functions.  Here's one:
>>
>> http://www.astrostatistics.psu.edu/su07/R/html/stats/html/Uniform.html
>>
>>
>>
>>> 3) numbers generated in the first set should be matched to numbers in
>>> the second set (row by row) so that the expected value of each couple
>>> of random numbers (i.e. of each lottery) is around to a given value
>>> (12.5 +/- 5, where 12.5 is the median value of the interval extremes).
>>
>>
>> Do you mean that the mean for the pair of numbers must be between 7.5 and
>> 17.5, inclusive?  That means the sum must be from 15 to 35.  Well, you are
>> in luck because if you make the numbers as you suggested above, that will
>> happen -- you don't have to do anything special to make it happen.
>>
>>
>>
>>> For the computation of the expected value, the probabilities in each
>>> lottery are ½ and ½.
>>
>>
>> For what outcome?  You lost me.
>>
>>
>>
>>> How do this? Any help given would be greatly appreciated.
>>
>>
>> I hope that helps.
>>
>> Mike
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
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