用于从估算数据进行描述性统计的用户定义函数问题

Question

我正在尝试编写一个函数来计算乘法估算数据帧 (mids) 中变量的均值和 SD。代码在函数外运行良好（如下面两个示例所示），但放在函数内时会产生不可靠的结果。尽管调用了 chl.

，该函数似乎仍在为 bmi 提供结果

感谢您对此问题的任何见解。最终我希望这个函数能够一次计算多个变量的均值和 SD（即 bmi 和 chl），但这可能是一个单独的问题。

library(mice, warn.conflicts = FALSE)
data(nhanes)
imp <- mice(nhanes, m = 3, print = FALSE, seed = 123)

# workflow that i want to automate
# from here: https://bookdown.org/mwheymans/bookmi/data-analysis-after-multiple-imputation.html
# example 1 - bmi
impdat <- mice::complete(imp, action = "long", include = FALSE)
pool_mean <- with(impdat, by(impdat, .imp, function(x) c(mean(x$bmi), sd(x$bmi))))
result <- (Reduce("+", pool_mean)/length(pool_mean))
print(result)
#> [1] 27.117333  3.980506
rm(impdat, pool_mean, result)

# example 2 - chl
impdat <- mice::complete(imp, action = "long", include = FALSE)
pool_mean <- with(impdat, by(impdat, .imp, function(x) c(mean(x$chl), sd(x$chl))))
result <- (Reduce("+", pool_mean)/length(pool_mean))
print(result)
#> [1] 195.10667  39.95247
rm(impdat, pool_mean, result)

# automating the workflow
automate <- function(a, b) {
  impdat <- mice::complete(a, action = "long", include = FALSE)
  pool_mean <- with(impdat, by(impdat, .imp, function(x) c(mean(x$b), sd(x$b))))
  result <- (Reduce("+", pool_mean)/length(pool_mean))
  print(result)
}

automate(a=imp, b=bmi) # looks correct ... ?
#> [1] 27.117333  3.980506
automate(a=imp, b=chl) # no, it isn't
#> [1] 27.117333  3.980506

Answer 1

这里有两个半问题：

b = bmi 看起来像一个对象 bmi，它在我们的全局环境中不存在。我们可以为此使用 deparse(susbtitute(x))，告诉函数等待评估。
访问函数$，参见?Extract：[[和$select都是列表的单个元素。主要区别在于 $ 不允许计算索引

automate <- function(a, b) {
  b <- deparse(substitute(b))
  impdat <- mice::complete(a, action = "long", include = FALSE)
  pool_mean <- with(impdat, by(impdat, .imp, function(x) c(mean(x[[b]]), sd(x[[b]]))))
  (Reduce("+", pool_mean)/length(pool_mean))
}
automate(a=imp, b=bmi)
[1] 27.117333  3.980506
automate(a=imp, b=chl)
[1] 195.10667  39.95247

要在变量列表上执行此操作，我们可以将其稍微重写为

automate_list <- function(a, ...){
  impdat <- mice::complete(a, action = "long", include = FALSE)
  lapply(list(...), function(x){
    x = as.name(x)
    pool_mean <- with(impdat, by(impdat, .imp, function(y) c(mean(y[[x]]), sd(y[[x]]))))
    Reduce("+", pool_mean)/length(pool_mean)
  }) |>
    setNames(list(...))
}

automate_list(imp, "bmi", "chl")
$bmi
[1] 27.117333  3.980506

$chl
[1] 195.10667  39.95247

用于从估算数据进行描述性统计的用户定义函数问题

Issue with user-defined function for descriptive statistics from imputed data

r

function

r-mice