[R] Help on percentage of random numbers for different classes

[Nordlund, Dan (DSHS/RDA)]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
> Behalf Of KABELI MEFANE
> Sent: Wednesday, September 09, 2009 4:06 PM
> To: R-help at r-project.org
> Subject: Re: [R] Help on percentage of random numbers for different classes
> 
> R-list
> 
> I am sorry for asking this stupid question, but i have been running in circles. I want
> to randomly generate a scaling point of between 1 and 10, for say hundred entries,
> where the first 10% percent is has rates between 2 and 7, the next 15% 3 and 7,
> 20% between 3 and 9, 20% between 3 and  10, 35% between 5 and 10. The
> problem is that i can only generate the usual 100 using runif function
> 
>  > y<-c(ceiling(10*runif(100)))
> > y
>   [1] 10  8  5  2  4  1  6  7  1  6  8  8  8  9  7  7  8  8  2  7  3 10  1  7  1
>  [26] 10  4  8  8  8  9  3  7  8  4  6  7  2  3  1  9  8  2  6  7  4  8  8  9  7
>  [51]  6  5  4  1  8  7  9  8 10  5  3  7  5  5  4  4  7  4 10  4  9  1  5 10 10
>  [76]  5  5 10  7  3  4  4  9 10  6  2  6  6  6  3  8  2  2  4  4 10  6  9  4  3
> 
> I just want to try to avoid small numbers as much as possible. I am open to
> suggestions, please please please.
> 
> Kabeli
> 
> 
If I understand you correctly, this might do what you want.  n is a vector with the number samples you want in each range, x is then minimum for each range and y is the maximum.  The function, s, samples from a given range, a specified number of times.  mapply applies the function using the first, second, ... elements in turn returning a list with the samples.  

n <- c(10,15,20,20,35)
x <- c(2,3,3,3,5)
y <- c(7,7,9,10,10)

s <- function(mn, mx, n) {sample(mn:mx, n, replace=TRUE)}
unlist(mapply(s, x, y, n))

Hope this is helpful,

Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA  98504-5204