CODEWITHSUNDEEP
r
Danilo Perl
Danilo Perl

Reputation: 69

R apply random values to dataframe by index

Guys I have the following code below where I simulate a number of poisson values ​​and for each value, simulate n exponential values ​​and allocate in the first n rows of the same column in the 'matrix' dataframe. Where ind are the values ​​obtained in each column of p that will be used to fill the first ind rows of each 'matrix' column, tamanho is the number of rows and cenarios is the number of columns.

p = matrix(data=rpois(1*cenarios, p*tamanho), nrow=1, ncol=cenarios)
matriz = matrix(NA, tamanho, cenarios)
matriz[ind] = rexp(nrow(ind), rate = 1/media)

So in case if my p is

4 3 0 5 ...

My matrix must be

x11 x12 0 x14 ...
x21 x22 0 x24 ...
x31 x32 0 x34 ...
x41   0 0 x44 ...
  0   0 0 x54 ...
  0   0 0   0 ...
  .   . .   . ...
  .   . .   . ...
  .   . .   . ...

Can anyone help me do this? Unfortunately my code is not producing this result and I don't know how to get it there. Thank you!

Upvotes: 0

Views: 91

Answers (1)

ekoam
ekoam

Reputation: 8844

Is this what you want?

cenarios <- 5
tamanho <- 6
media <- 10
p <- 0.5

get_idx <- function(p) {
  dim(p) <- NULL
  cbind(
    row = unlist(lapply(p, seq_len)), 
    col = inverse.rle(list(lengths = p, values = seq_along(p)))
  )
}

set.seed(14)
p = matrix(data=rpois(1*cenarios, p*tamanho), nrow=1, ncol=cenarios)
matriz = matrix(0, p[1L, max.col(p)], cenarios)
ind = get_idx(p)
matriz[ind] = rexp(nrow(ind), rate = 1/media)

> matriz
          [,1]      [,2]      [,3]      [,4]       [,5]
[1,] 0.2294774 12.197561 11.055460  4.998411  0.4666982
[2,] 2.9696347  1.135306  3.467462  2.379091  3.7448796
[3,] 0.0000000  5.127104  2.432433 12.324723 23.3540920
[4,] 0.0000000  0.000000 13.716225  0.000000  6.2265665
[5,] 0.0000000  0.000000  2.353816  0.000000 14.8491943
[6,] 0.0000000  0.000000  3.805390  0.000000  0.8669793
[7,] 0.0000000  0.000000  0.000000  0.000000  1.0776727

Upvotes: 1

Related Questions