Hello,
Inline.
Às 16:08 de 21/04/2025, Rui Barradas escreveu:
Às 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?
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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
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