[R] Generation of uniform random numbers

[Gavin Simpson]

Sarah,

Here's a version using two nested loops:

rate_number = matrix(c(5, 15, 60, 15, 5, 0, 20, 60, 20,0, 10, 20, 40,
20, 10), nrow = 5, ncol = 3)

range_mat = matrix(c(6.25, 6.75, 7.25, 8.75, 9.25, 9.75, 8.5, 9, 9.5,
10.5, 11, 11.5, 4.25, 4.75, 5.25, 5.75, 6.25, 6.75), nrow = 6, ncol = 3)

set.seed(123)
res <- vector(mode = "list", length = NCOL(rate_number))
rateSum <- colSums(rate_number)
for(i in seq_len(NCOL(rate_number))) {
    res[[i]] <- numeric(length = rateSum[i])
    rates <- rate_number[,i]
    rates <- rates[(want <- which(rates > 0))]
    for(j in seq_along(rates)) {
        if(j == 1) {
            from <- 1
            to <- rates[1]
        } else {
            from <- sum(rates[1:(j-1)]) + 1
            to <- sum(rates[1:j])
        }
        res[[i]][from:to] <- runif(rates[j],
                                   min = range_mat[want[j],i],
                                   max = range_mat[want[j]+1, i])
    }
}
str(res)
head(res)

Not the most elegant code but it works...

Most of the fiddling about in there is to work round the fact that you
have 0's in some cells of rate_number and I wanted to avoid
concatenating vectors to enlarge them, so allocate storage first.

HTH

G

On Fri, 2010-09-03 at 03:32 -0700, Sarah Sanchez wrote:

> Dear R helpers
> 
> I have following dataset
> 
> rate_number = matrix(c(5, 15, 60, 15, 5, 0, 20, 60, 20,0, 10, 20, 40, 20, 10), nrow = 5, ncol = 3)
> 
> range_mat = matrix(c(6.25, 6.75, 7.25, 8.75, 9.25, 9.75, 8.5, 9, 9.5, 10.5, 11, 11.5, 4.25, 4.75, 5.25, 5.75, 6.25, 6.75), nrow = 6, ncol = 3)
> 
> > rate_number
>  [,1] [,2] [,3]
> [1,] 5 0 10
> [2,] 15 20 20
> [3,] 60 60 40
> [4,] 15 20 20
> [5,] 5 0 10
> 
> > range_mat
>  [,1]   [,2] [,3]
> [1,] 6.25  8.5 4.25
> [2,] 6.75 9.0 4.75
> [3,] 7.25 9.5 5.25
> [4,] 8.75 10.5 5.75
> [5,] 9.25 11.0 6.25
> [6,] 9.75 11.5 6.75
> 
> My problem is to generate random numbers in line with rate_number and using the range_mat. E.g.
> 
> I need to generate (5, 15, 60, 15, 5 i.e. the first column of rate_number) uniform random numbers (using 1st column of range_mat) s.t the first 5 numbers will be in the range (6.25 - 6.75), next 15 numbers should be in the range (6.75 to 7.25), next 60 numbers should be in the range (7.25 to 8.75), next 15 numbers in the range (8.75 to 9.25) and last 5 numbers in the range (9.25 to 9.75).
> 
> Similarily, I need to generate (0, 20, 60, 20, 0 i.e. 2nd column of rate_number) uniform random numbers in the range (using 2nd column of range_mat) i.e. (8.5 to 9), (9 to 9.5), (9.5 to 10.5), (10.5 to 11), (11 to 11.5) respectively.
> 
> I could have generated these random numbersIndividually using runif, but main problem is range_number could be anything i.e. there may be 50 rates but for each rate, no of rate combination will always be 5 i.e. rate_number will always have 5 rows only and also range_mat will always have 6 rows only.
> 
> I tried writing loops and even tapply etc. but just can't get through.
> 
> I sincerely request you to kindly guide me.
> 
> Regards
> 
> Sarah 
> 
> 
> 
> 
> 
> 
>       
> 	[[alternative HTML version deleted]]
> 
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