CODEWITHSUNDEEP
rdplyr
user51966
user51966

Reputation: 1057

Creating a tibble and randomization

I want to create a tibble with ID (iter) and randomly generated data.

   iter data
  <int> <list>
1     1 <dbl [5]>
2     2 <dbl [5]>
3     3 <dbl [5]>

I tried two types of codes and only one of them gives the expected result, but I am not sure why it is, because the only difference is generating data inside tibble() or not.

iter <- 2 ; n <- 5 ; mu <- 1
gen_data <- function(x){  # randomly draw from Exponential function
    return(rexp(n, rate=1/mu))
}

# Works (different values each time)
data <- lapply(1:iter, gen_data)
tibble(iter = 1:iter,
             data = data) %>% unnest(data)

# Doesn't work (+ there is a warning)
tibble(iter = 1:iter,
             data = lapply(1:iter, gen_data)) %>% unnest(data)

Upvotes: 2

Views: 70

Answers (1)

Nate
Nate

Reputation: 10671

When you call lapply() in the second expample that doesn't work, you need to be referencing iter only by it's name instead of trying to re-build a vector. 

tibble(iter = 1:iter,
       data = lapply(iter, gen_data)) %>% unnest(data)

This is because tibble() is looking for variables by name within it's context and iter already exists there as c(1,2). The warning comes from you passing two element to : which complains, then moves ahead using the first element.

Upvotes: 3

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