r - 在存在可选参数的情况下如何处理省略号（...）？

Question

当我在函数定义中使用可选参数时，省略号有问题。为了澄清，我定义了以下函数：

func1 <- function (x) (x-2)^2

func3 <- function (fun, arg.curve.user){
  arg.curve.user$expr <-  substitute(func1)
  arg.curve.default <- list(col = "blue", n = 1000, main = "This is a test")
  arg.curve <- modifyList (arg.curve.default, arg.curve.user)
  do.call("curve", arg.curve)
}

# optimizes func1 and call func2 to plot func1
func2 <- function (lb, ub, n.restarts = 5, n.sim = 10, ...){
  arg.curve.user <- as.list(substitute(list(...)))
  output <- gosolnp(fun = func1, LB = lb, UB = ub,  n.restarts =  n.restarts, 
  n.sim =  n.sim)$par
  func3(fun = func1, arg.curve.user = arg.curve.user)
   return(output)
}

通过调用 func2，对 func1 进行优化，并通过 func3 调用（需要Rsolnp包）进行绘制。

func2 ( lb = 0, ub = 8, n.restarts = 5, n.sim = 10, n = 200, from = 0, to = 8)

但是假设用户拼写错误n.restarts并写道nrestarts：

func2 ( lb = 0, ub = 8, nrestarts = 5, n.sim = 10, n = 200, from = 0, to = 8)

在这种情况下，我希望 R 实施以下计划来处理 的缺失n.restarts：

1. 将默认值（即 5）分配给 n.restarts 作为可选参数
2. 最后声明一个警告：“nrestarts”不是图形参数

但这不会发生，而是 R 将 n (200) 的值分配给 n.restarts！

谁能帮我解决这个问题？

非常感谢

Answer 1

当用户未提供参数时，它部分匹配n参数。n.restarts相反，与@Andrie 的建议相反（当然，它会起作用），有一种机制可以让你以你有的方式继续使用 argumentn和 and n.restarts。诀窍是在. _ ...

func2 <- function (lb, ub, ..., n.restarts = 5, n.sim = 10){
  writeLines(paste("Value of `n.restarts` is", n.restarts))
  arg.curve.user <- as.list(substitute(list(...)))
  output <- gosolnp(fun = func1, LB = lb, UB = ub,  n.restarts =  n.restarts, 
                    n.sim =  n.sim)$par
  func3(fun = func1, arg.curve.user = arg.curve.user)
  output
}

在使用中，这给出了：

> func2 (lb = 0, ub = 8, n.restarts = 2, n.sim = 10, n = 200,
+        from = 0, to = 8)
Value of `n.restarts` is 2          <---- Here!

Iter: 1 fn: 6.926e-15    Pars:  2.00000
Iter: 2 fn: 2.501e-15    Pars:  2.00000
solnp--> Completed in 2 iterations

Iter: 1 fn: 8.336e-16    Pars:  2.00000
Iter: 2 fn: 8.336e-16    Pars:  2.00000
solnp--> Completed in 2 iterations
[1] 2
> func2 (lb = 0, ub = 8, nrestarts = 2, n.sim = 10, n = 200,
+        from = 0, to = 8)
Value of `n.restarts` is 5          <---- Here! Default

Iter: 1 fn: 2.83e-15     Pars:  2.00000
Iter: 2 fn: 2.5e-15  Pars:  2.00000
solnp--> Completed in 2 iterations

Iter: 1 fn: 2.037e-15    Pars:  2.00000
Iter: 2 fn: 2.037e-15    Pars:  2.00000
solnp--> Completed in 2 iterations

Iter: 1 fn: 1.087e-15    Pars:  2.00000
Iter: 2 fn: 1.087e-15    Pars:  2.00000
solnp--> Completed in 2 iterations

Iter: 1 fn: 8.558e-16    Pars:  2.00000
Iter: 2 fn: 8.558e-16    Pars:  2.00000
solnp--> Completed in 2 iterations

Iter: 1 fn: 7.147e-16    Pars:  2.00000
Iter: 2 fn: 7.147e-16    Pars:  2.00000
solnp--> Completed in 2 iterations
[1] 2
Warning messages:
1: In plot.window(...) : "nrestarts" is not a graphical parameter
2: In plot.xy(xy, type, ...) : "nrestarts" is not a graphical parameter
3: In axis(side = side, at = at, labels = labels, ...) :
  "nrestarts" is not a graphical parameter
4: In axis(side = side, at = at, labels = labels, ...) :
  "nrestarts" is not a graphical parameter
5: In box(...) : "nrestarts" is not a graphical parameter
6: In title(...) : "nrestarts" is not a graphical parameter

Answer 2

如果您坚持定期进行参数评估，您更有可能立即收到警告。同样，您不需要使用特殊的评估来获得您想要的行为。使用非标准评估是一个坏主意，因为您不太可能完全重现 R 的默认行为，从而给您和您的用户带来细微的错误。

library(Rsolnp)

func1 <- function (x) (x-2)^2

func3 <- function (fun, col = "blue", n = 1000, main = "This is a test", ...){
  curve(func1, ..., n = n, col = col, main = main)
}

# optimizes func1 and call func2 to plot func1
func2 <- function (lb, ub, n.restarts = 5, n.sim = 10, ...){
  output <- gosolnp(fun = func1, LB = lb, UB = ub, n.restarts = n.restarts, 
  n.sim =  n.sim)$par
  func3(fun = func1, ...)
  return(output)
}

然后当你运行：

func2 ( lb = 0, ub = 8, nrestarts = 5, n.sim = 10, n = 200, from = 0, to = 8)

您会收到以下警告

Warning messages:
1: In plot.window(...) : "nrestarts" is not a graphical parameter
2: In plot.xy(xy, type, ...) : "nrestarts" is not a graphical parameter
3: In axis(side = side, at = at, labels = labels, ...) :
  "nrestarts" is not a graphical parameter
4: In axis(side = side, at = at, labels = labels, ...) :
  "nrestarts" is not a graphical parameter
5: In box(...) : "nrestarts" is not a graphical parameter
6: In title(...) : "nrestarts" is not a graphical parameter