在一行中在 LHS 上分配多个新变量 [英] Assign multiple new variables on LHS in a single line

问题描述

我想在 R 中的一行中分配多个变量.可以这样做吗?

I want to assign multiple variables in a single line in R. Is it possible to do something like this?

values # initialize some vector of values
(a, b) = values[c(2,4)] # assign a and b to values at 2 and 4 indices of 'values'

通常我想在一行中分配大约 5-6 个变量，而不是多行.有其他选择吗?

Typically I want to assign about 5-6 variables in a single line, instead of having multiple lines. Is there an alternative?

推荐答案

解决问题博客

这是取自那里，做了非常小的修改.

This is taken from there, with very minor modifications.

使用以下三个功能(加上一个允许不同大小的列表)

USING THE FOLLOWING THREE FUNCTIONS (Plus one for allowing for lists of different sizes)

# Generic form
'%=%' = function(l, r, ...) UseMethod('%=%')

# Binary Operator
'%=%.lbunch' = function(l, r, ...) {
  Envir = as.environment(-1)

  if (length(r) > length(l))
    warning("RHS has more args than LHS. Only first", length(l), "used.")

  if (length(l) > length(r))  {
    warning("LHS has more args than RHS. RHS will be repeated.")
    r <- extendToMatch(r, l)
  }

  for (II in 1:length(l)) {
    do.call('<-', list(l[[II]], r[[II]]), envir=Envir)
  }
}

# Used if LHS is larger than RHS
extendToMatch <- function(source, destin) {
  s <- length(source)
  d <- length(destin)

  # Assume that destin is a length when it is a single number and source is not
  if(d==1 && s>1 && !is.null(as.numeric(destin)))
    d <- destin

  dif <- d - s
  if (dif > 0) {
    source <- rep(source, ceiling(d/s))[1:d]
  }
  return (source)
}

# Grouping the left hand side
g = function(...) {
  List = as.list(substitute(list(...)))[-1L]
  class(List) = 'lbunch'
  return(List)
}

使用新函数g()对左侧进行分组右手边应该是一个向量或一个列表使用新创建的二元运算符 %=%

Group the left hand side using the new function g() The right hand side should be a vector or a list Use the newly-created binary operator %=%

# Example Call;  Note the use of g()  AND  `%=%`
#     Right-hand side can be a list or vector
g(a, b, c)  %=%  list("hello", 123, list("apples, oranges"))

g(d, e, f) %=%  101:103

# Results: 
> a
[1] "hello"
> b
[1] 123
> c
[[1]]
[1] "apples, oranges"

> d
[1] 101
> e
[1] 102
> f
[1] 103

<人力资源>

较长的左侧

g(x, y, z) %=% list("first", "second")
#   Warning message:
#   In `%=%.lbunch`(g(x, y, z), list("first", "second")) :
#     LHS has more args than RHS. RHS will be repeated.
> x
[1] "first"
> y
[1] "second"
> z
[1] "first"

较长的右手边

g(j, k) %=% list("first", "second", "third")
#   Warning message:
#   In `%=%.lbunch`(g(j, k), list("first", "second", "third")) :
#     RHS has more args than LHS. Only first2used.
> j
[1] "first"
> k
[1] "second"

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