汇总返回多个值的函数的非嵌套结果

Dieter Menne 发表于 Dev

迪特·曼尼（Dieter Menne）

“想要的”结果由下面的“执行”功能给出。我以为我可以通过使用一些嵌套来获得相同的效果，但是无法使其正常工作。

library(dplyr)
library(tidyr)

# Function rr is given
rr = function(x){
  # This should be an expensive and possibly random function
  r = range(x + rnorm(length(x),0.1))
#  setNames(r, c("min", "max")) # fails, expecting single value
#  list(min = r[1], max= r[2]) # fails
  list(r) # Works, but result is in "long" form without min/max
}

# Works, but syntactically awkward
iris %>% group_by(Species) %>%
  do( {
    r = rr(.$Sepal.Width)[[1]]
    data_frame(min = r[1], max = r[2])
  })

# This give the long format, but without column
# names min/max
iris %>% group_by(Species) %>%
  summarize(
    range = rr(Sepal.Length)
  ) %>% unnest(range)

一个孩子

Unnest()会始终以“长”格式取消列出嵌套列，但spread()如果您创建key列，则可以用来获取所需的输出。

library(dplyr)
library(tidyr)

iris %>%
  group_by(Species) %>%
  summarize(range = rr(Sepal.Length)) %>% 
  unnest(range) %>% mutate(newcols = rep(c("min", "max"), 3)) %>%
  spread(newcols, range)
#     Species      max      min
#      (fctr)    (dbl)    (dbl)
#1     setosa 7.636698 3.292692
#2 versicolor 9.792319 3.337382
#3  virginica 9.810723 3.367066

本文收集自互联网，转载请注明来源。

如有侵权，请联系[email protected] 删除。