Brian Smith
2025-Apr-22 11:39 UTC
[R] Generate random vectors (continuous number) with a fixed sum
Hi Rui,
Many thanks for your time and insight.
However, I am not sure if I could understand the code. Below is what I
tried based on your code
library(Surrogate)
a <- c(0.015, 0.005)
b <- c(0.070, 0.045)
set.seed(2025)
res <- mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m),
MoreArgs = list(s = 0.05528650577311, n = 2, m = 10000), a, b)
res1 = res[[1]]
res2 = res[[2]]
apply(res1, 1, min) > a ## [1] TRUE TRUE
apply(res2, 1, min) > a ## [1] FALSE TRUE
I could not understand what basically 2 blocks of res signify? Which
one I should take as final simulation of the vector? If I take the
first block then the lower bound condition is fulfilled, but not with
the second block. However with the both blocks, the total equals s is
satisfying.
I appreciate your further insight.
Thanks and regards,
On Mon, 21 Apr 2025 at 20:43, Rui Barradas <ruipbarradas at sapo.pt>
wrote:>
> Hello,
>
> Inline.
>
> ?s 16:08 de 21/04/2025, Rui Barradas escreveu:
> > ?s 15:27 de 21/04/2025, Brian Smith escreveu:
> >> Hi,
> >>
> >> There is a function called RandVec in the package Surrogate which
can
> >> generate andom vectors (continuous number) with a fixed sum
> >>
> >> The help page of this function states that:
> >>
> >> a
> >>
> >> The function RandVec generates an n by m matrix x. Each of the m
> >> columns contain n random values lying in the interval [a,b]. The
> >> argument a specifies the lower limit of the interval. Default 0.
> >>
> >> b
> >>
> >> The argument b specifies the upper limit of the interval. Default
1.
> >>
> >> However in my case, the lower and upper limits are not same. For
> >> example, if I need to draw a pair of number x, y, such that x + y
= 1,
> >> then the lower and upper limits are different.
> >>
> >> I tried with below code
> >>
> >> library(Surrogate)
> >>
> >> RandVec(a=c(0.1, 0.2), b=c(0.2, 0.8), s=1, n=2, m=5)$RandVecOutput
> >>
> >> This generates error with message
> >>
> >> Error in if (b - a == 0) { : the condition has length > 1
> >>
> >> Is there any way to generate the numbers with different lower and
> >> upper limits?
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
https://www.R-project.org/posting-
> >> guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> > Hello,
> >
> > Use ?mapply to cycle through all values of a and b.
> > Note that the output matrices are transposed, the random vectors are
the
> > rows.
> Sorry, this is not true. The columns are the random vectors, as
> documented. An example setting the RNG seed, for reproducibility.
>
>
> library(Surrogate)
>
> a <- c(0.1, 0.2)
> b <- c(0.2, 0.8)
> set.seed(2025)
> res <- mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m),
> MoreArgs = list(s = 1, n = 2, m = 5), a, b)
>
> res
> #> $RandVecOutput
> #> [,1] [,2] [,3] [,4] [,5]
> #> [1,] 0.146079 0.1649319 0.1413759 0.257086 0.1715478
> #> [2,] 0.253921 0.2350681 0.2586241 0.142914 0.2284522
> #>
> #> $RandVecOutput
> #> [,1] [,2] [,3] [,4] [,5]
> #> [1,] 0.5930918 0.2154583 0.6915523 0.7167089 0.3617918
> #> [2,] 0.4069082 0.7845417 0.3084477 0.2832911 0.6382082
>
> lapply(res, colSums)
> #> $RandVecOutput
> #> [1] 0.4 0.4 0.4 0.4 0.4
> #>
> #> $RandVecOutput
> #> [1] 1 1 1 1 1
>
>
> Hope this helps,
>
> Rui Barradas
> >
> >
> > library(Surrogate)
> >
> > a <- c(0.1, 0.2)
> > b <- c(0.2, 0.8)
> > mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m),
> > MoreArgs = list(s = 1, n = 2, m = 5), a, b)
> > #> $RandVecOutput
> > #> [,1] [,2] [,3] [,4] [,5]
> > #> [1,] 0.2004363 0.1552328 0.2391742 0.1744857 0.1949236
> > #> [2,] 0.1995637 0.2447672 0.1608258 0.2255143 0.2050764
> > #>
> > #> $RandVecOutput
> > #> [,1] [,2] [,3] [,4] [,5]
> > #> [1,] 0.2157416 0.4691191 0.5067447 0.7749258 0.7728955
> > #> [2,] 0.7842584 0.5308809 0.4932553 0.2250742 0.2271045
> >
> >
> > Hope this helps,
> >
> > Rui Barradas
> >
> >
>
>
> --
> Este e-mail foi analisado pelo software antiv?rus AVG para verificar a
presen?a de v?rus.
> www.avg.com
Rui Barradas
2025-Apr-22 16:32 UTC
[R] Generate random vectors (continuous number) with a fixed sum
?s 12:39 de 22/04/2025, Brian Smith escreveu:> Hi Rui, > > Many thanks for your time and insight. > > However, I am not sure if I could understand the code. Below is what I > tried based on your code > > library(Surrogate) > a <- c(0.015, 0.005) > b <- c(0.070, 0.045) > set.seed(2025) > res <- mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m), > MoreArgs = list(s = 0.05528650577311, n = 2, m = 10000), a, b) > > res1 = res[[1]] > res2 = res[[2]] > > apply(res1, 1, min) > a ## [1] TRUE TRUE > apply(res2, 1, min) > a ## [1] FALSE TRUE > > I could not understand what basically 2 blocks of res signify? Which > one I should take as final simulation of the vector? If I take the > first block then the lower bound condition is fulfilled, but not with > the second block. However with the both blocks, the total equals s is > satisfying. > > I appreciate your further insight. > > Thanks and regards, > > On Mon, 21 Apr 2025 at 20:43, Rui Barradas <ruipbarradas at sapo.pt> wrote: >> >> Hello, >> >> Inline. >> >> ?s 16:08 de 21/04/2025, Rui Barradas escreveu: >>> ?s 15:27 de 21/04/2025, Brian Smith escreveu: >>>> Hi, >>>> >>>> There is a function called RandVec in the package Surrogate which can >>>> generate andom vectors (continuous number) with a fixed sum >>>> >>>> The help page of this function states that: >>>> >>>> a >>>> >>>> The function RandVec generates an n by m matrix x. Each of the m >>>> columns contain n random values lying in the interval [a,b]. The >>>> argument a specifies the lower limit of the interval. Default 0. >>>> >>>> b >>>> >>>> The argument b specifies the upper limit of the interval. Default 1. >>>> >>>> However in my case, the lower and upper limits are not same. For >>>> example, if I need to draw a pair of number x, y, such that x + y = 1, >>>> then the lower and upper limits are different. >>>> >>>> I tried with below code >>>> >>>> library(Surrogate) >>>> >>>> RandVec(a=c(0.1, 0.2), b=c(0.2, 0.8), s=1, n=2, m=5)$RandVecOutput >>>> >>>> This generates error with message >>>> >>>> Error in if (b - a == 0) { : the condition has length > 1 >>>> >>>> Is there any way to generate the numbers with different lower and >>>> upper limits? >>>> >>>> ______________________________________________ >>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>> PLEASE do read the posting guide https://www.R-project.org/posting- >>>> guide.html >>>> and provide commented, minimal, self-contained, reproducible code. >>> Hello, >>> >>> Use ?mapply to cycle through all values of a and b. >>> Note that the output matrices are transposed, the random vectors are the >>> rows. >> Sorry, this is not true. The columns are the random vectors, as >> documented. An example setting the RNG seed, for reproducibility. >> >> >> library(Surrogate) >> >> a <- c(0.1, 0.2) >> b <- c(0.2, 0.8) >> set.seed(2025) >> res <- mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m), >> MoreArgs = list(s = 1, n = 2, m = 5), a, b) >> >> res >> #> $RandVecOutput >> #> [,1] [,2] [,3] [,4] [,5] >> #> [1,] 0.146079 0.1649319 0.1413759 0.257086 0.1715478 >> #> [2,] 0.253921 0.2350681 0.2586241 0.142914 0.2284522 >> #> >> #> $RandVecOutput >> #> [,1] [,2] [,3] [,4] [,5] >> #> [1,] 0.5930918 0.2154583 0.6915523 0.7167089 0.3617918 >> #> [2,] 0.4069082 0.7845417 0.3084477 0.2832911 0.6382082 >> >> lapply(res, colSums) >> #> $RandVecOutput >> #> [1] 0.4 0.4 0.4 0.4 0.4 >> #> >> #> $RandVecOutput >> #> [1] 1 1 1 1 1 >> >> >> Hope this helps, >> >> Rui Barradas >>> >>> >>> library(Surrogate) >>> >>> a <- c(0.1, 0.2) >>> b <- c(0.2, 0.8) >>> mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m), >>> MoreArgs = list(s = 1, n = 2, m = 5), a, b) >>> #> $RandVecOutput >>> #> [,1] [,2] [,3] [,4] [,5] >>> #> [1,] 0.2004363 0.1552328 0.2391742 0.1744857 0.1949236 >>> #> [2,] 0.1995637 0.2447672 0.1608258 0.2255143 0.2050764 >>> #> >>> #> $RandVecOutput >>> #> [,1] [,2] [,3] [,4] [,5] >>> #> [1,] 0.2157416 0.4691191 0.5067447 0.7749258 0.7728955 >>> #> [2,] 0.7842584 0.5308809 0.4932553 0.2250742 0.2271045 >>> >>> >>> Hope this helps, >>> >>> Rui Barradas >>> >>> >> >> >> -- >> Este e-mail foi analisado pelo software antiv?rus AVG para verificar a presen?a de v?rus. >> www.avg.comHello, The two blocks of res are the two random matrices, one for each combination of (a,b). mapply passes each of the values in its arguments list (the ellipses in the help page) and computes the anonymous function with the pairs (a[1], b[1]), (a[2], b[2]). Since a and b are two elements vectors the output res is a two members named list. Your error is to compare the result of apply(res2, 1, min) to a, when you should compare to a[2]. See the code below. library(Surrogate) a <- c(0.015, 0.005) b <- c(0.070, 0.045) set.seed(2025) res <- mapply(\(a, b, s, n, m) RandVec(a, b, s, n, m), MoreArgs = list(s = 0.05528650577311, n = 2, m = 10000), a, b) res1 = res[[1]] res2 = res[[2]] # first check that the sums are correct # these sums should be s = 0.05528650577311, up to floating-point accuracy lapply(res, \(x) colSums(x[, 1:5]) |> print(digits = 14L)) #> [1] 0.05528650577311 0.05528650577311 0.05528650577311 0.05528650577311 #> [5] 0.05528650577311 #> [1] 0.05528650577311 0.05528650577311 0.05528650577311 0.05528650577311 #> [5] 0.05528650577311 #> $RandVecOutput #> [1] 0.05528651 0.05528651 0.05528651 0.05528651 0.05528651 #> #> $RandVecOutput #> [1] 0.05528651 0.05528651 0.05528651 0.05528651 0.05528651 # now check the min and max apply(res1, 1, min) > a[1L] ## [1] TRUE TRUE #> [1] TRUE TRUE apply(res2, 1, min) > a[2L] ## [1] TRUE TRUE #> [1] TRUE TRUE apply(res1, 1, max) < b[1L] ## [1] TRUE TRUE #> [1] TRUE TRUE apply(res2, 1, max) < b[2L] ## [1] TRUE TRUE #> [1] TRUE TRUE Which one should you take as final simulation of the vector? Both. The first matrix values are bounded by c(a[1], b[1]) with column sums equal to s. The second matrix values are bounded by c(a[2], b[2]) with column sums also equal to s. Hoep this helps, Rui Barradas