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Question

我想将可管理的函数（magrittr / dplyr）总结为更短的函数 - ＆＃34; blocks＆＃34; （希望有更多可读代码）。例如：

library(dplyr)

d <- tbl_df(data.frame(A = rep(LETTERS[2:5], each = 5),
                       M = rep(letters[1:2], times = 10),
                       X = round(rnorm(20, 10, 2), 1)))

# I want to replace this
# ----------------------
d %>%
  group_by(A) %>%
  summarise(X = mean(X)) -> d_test_1

# with this
# ---------
my_mean <- function(d, by_var, x) {
  expr <- substitute(by_var) # group variable, seems ok
  expr_2 <- substitute(expression(x = mean(x))) # calculate mean
  print(deparse(expr_2))
  # problem: x = mean(x) is only substituted to x = mean(X) .. 1 capital x, should be 2
  expr_3 <- parse(text = paste(deparse(substitute(x)), "=mean(", 
                               deparse(substitute(x)), ")"))
  print(deparse(expr_3))
  # expr_3 does not work either
  d %>%
    group_by(eval(expr)) %>%
    #summarise(X = mean(X)) -> d # uses right group variable
    summarise(eval(expr_3)) -> d # uses wrong group variable <> side-effect of "expr"?
  invisible(d)
}

# this is the short version I am after
d %>%
  my_mean(A, X) -> d_test_2
d_test_1
d_test_2

Thx＆amp;亲切的问候

Answer 1

也许别人不知道在哪里看：

const std::vector<std::map<Id, std::vector<Data>>> *const DataSets
{
    &object.data1,
    &object.data2,
    &object.data3,
    &object.data4
};