将运算符分配给R变量 [英] Assigning operators into an R variable

问题描述

我正在尝试创建一个函数，用户可以选择想要使用的运算符，从而产生不同的输出.但是我似乎无法使其正常工作.我知道我们不能将运算符分配到R对象中，然后根据R对象名称将其用作运算符.有办法吗?还是编写函数的更好方法?

I am trying to create a function where users can select the operator they want to use, which result in a different output. But I can't seem to get it to work. I know that we can't assign operators into an R object and then use it as an operator based on the R object name. Is there a way I could do this? Or perhaps a better way to write the function?

test <- function(items, operator = "+"){
bank_alpha <- matrix(ncol=6)
colnames(bank_alpha) <- colnames(bank_alpha, do.NULL = FALSE, prefix = "Q")
colnames(bank_alpha)[6] <- "A"
alphabet <- LETTERS[seq(1:26)]

 for (i in 1:items) {
  item <- c(alphabet[i], alphabet[i operator 1], alphabet[i operator  2], alphabet[i operator  3], alphabet[i operator  4], alphabet[i operator 5])
  bank_alpha <- rbind(bank_alpha, item)
  bank_alpha <- na.omit(bank_alpha)
}
return(bank_alpha)
}

  test(items=4, operator = "-") 

推荐答案

签出do.call，它将函数名作为参数.使用

Check out do.call, which takes the name of a function as an argument. With

operator <- "+"
do.call(operator, list(2,3)

您将得到 5 作为结果.

在您的示例中:

test <- function(items, operator = "+"){
  bank_alpha <- matrix(ncol=6)
  colnames(bank_alpha) <- colnames(bank_alpha, do.NULL = FALSE, prefix = "Q")
  colnames(bank_alpha)[6] <- "A"
  alphabet <- LETTERS[seq(1:26)]

  for (i in 1:items) {
    item <- c(alphabet[i], alphabet[do.call(operator, list(i,1))], alphabet[do.call(operator, list(i,2))], alphabet[do.call(operator, list(i,3))], alphabet[do.call(operator, list(i,4))], alphabet[do.call(operator, list(i,5))])
    bank_alpha <- rbind(bank_alpha, item)
    bank_alpha <- na.omit(bank_alpha)
  }
  return(bank_alpha)
}

test(items=4, operator = "*") 

当心，在这种情况下，-"没有意义.

Beware, "-" doesn't make sense in this case.

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