将 rpois 和 rnbinom 与 dplyr 命令结合使用

Question

我试图在小标题中生成随机数，其中不同类别的项目分布不同。我运气不太好。这是代码及其产生的错误：

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library(dplyr)\n\nletters <- tibble(letter = c(rep("A", 5), rep("B", 5), rep("C", 5) ))\n\nletters %>%\n  rowwise() %>%\n  mutate(Proj = case_when(\n    letter == "A" ~ rpois(1, lambda = .7746),\n    letter == "B" ~ rnbinom(1, size = 3.3848, mu = 1.2),\n    letter == "C" ~ rpois(1, lambda = .5057)\n  ))\n\n#> Error in `mutate()`:\n#> ! Problem while computing `Proj = case_when(...)`.\n#> \xe2\x84\xb9 The error occurred in row 1.\n#> Caused by error in `` names(message) <- `*vtmp*` ``:\n#> ! \'names\' attribute [1] must be the same length as the vector [0]\n

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有趣的是，如果我使用连续分布而不是离散分布，代码就可以正常工作。

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library(dplyr)\n\nletters <- tibble(letter = c(rep("A", 5), rep("B", 5), rep("C", 5) ))\n\nletters %>%\n  rowwise() %>%\n  mutate(Proj = case_when(\n    letter == "A" ~ rweibull(1, shape = 2.3487, scale = 8.174),\n    letter == "B" ~ rexp(1, rate = .0442),\n    letter == "C" ~ rnorm(1, mean = 0, sd = 1)\n  ))\n\n#> # A tibble: 15 \xc3\x97 2\n#> # Rowwise: \n#>    letter   Proj\n#>    <chr>   <dbl>\n#>  1 A       9.82 \n#>  2 A       7.72 \n#>  3 A      12.9  \n#>  4 A       7.81 \n#>  5 A       6.44 \n#>  6 B      10.4  \n#>  7 B       3.14 \n#>  8 B       1.48 \n#>  9 B      28.7  \n#> 10 B      11.0  \n#> 11 C      -0.378\n#> 12 C      -0.340\n#> 13 C       1.81 \n#> 14 C       1.03 \n#> 15 C      -0.679\n

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^{由reprex 包(v2.0.1)于 2022-07-29 创建}

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这里发生了什么？

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Answer 1

rpois返回一个整数。rnbinom返回一个双精度数。的文档case_when说：

      The LHS must evaluate to a logical vector. The RHS does not
      need to be logical, but all RHSs must evaluate to the same
      type of vector.

这就是导致问题的原因。要么将 rnbinom 的输出显式转换为整数，要么将 rpois 的输出显式转换为数值。