if else停止条件

Question

我有一个关于石头，布，剪刀，蜥蜴，斯波克游戏的问题。我有以下代码

    dataTable <- matrix(data = NA, nrow = 25, ncol = 3, byrow = TRUE)

dataTable <- as.data.frame(dataTable)
colnames(dataTable) <- c("Player-1", "Player-2", "Outcome")

## Fill in columns

dataTable[, 1] <- c(rep("Rock", 5), rep("Paper", 5), rep("Scissors", 5), 
                    rep("Lizard", 5), rep("Spock", 5))

dataTable[, 2] <- c(rep(c("Rock", "Paper", "Scissors", "Lizard", "Spock"), 5))
# Filling In The Outcome Column:

outcome_col <- c("Draw!", "Player 2 Wins!", "Player 1 Wins!", "Player 1 Wins!", "Player 2 Wins!",
                 "Player 1 Wins!", "Draw!", "Player 2 Wins!", "Player 2 Wins!", "Player 1 Wins!",
                 "Player 2 Wins!", "Player 1 Wins!", "Draw!", "Player 1 Wins!", "Player 2 Wins!",
                 "Player 2 Wins!", "Player 1 Wins!", "Player 2 Wins!", "Draw!", "Player 1 Wins!",
                 "Player 1 Wins!", "Player 2 Wins!", "Player 1 Wins!", "Player 2 Wins!", "Draw!")


# Place outcome_col as third column and convert as factors:


dataTable[, 3] <- as.factor(outcome_col)



sheldon_game<-function(A,B){
  for (i in 1:nrow(dataTable)){
    if (A!=dataTable[i,1] & B!=dataTable[i,2]){
      stop("Parameters out of bound")
    } else 
      if (A==dataTable[i,1] & B==dataTable[i,2]){
      res<-dataTable[i,3]
    }
  }
  return(res)
  }

sheldon_game("Scissors","Paper")

在最后一个函数sheldon_game中，如果插入了(岩石，纸张，剪刀，蜥蜴，斯波克)以外的错误信息，我想打印错误消息。但是当参数在列表中时，它会不断地以错误消息的形式显示结果。

Answer 1

问题是，您正在测试每一行上是否有匹配，并且由于输入数据将只匹配一行，因此您总是得到错误消息。您的代码可以按如下方式修改：

sheldon_game<-function(A,B){
  for (i in 1:nrow(dataTable)){
    if (! A %in% unique(dataTable[ ,1]) | ! B %in% unique(dataTable[ ,2])){
      stop("Parameters out of bound")
    } else 
      if (A==dataTable[i,1] & B==dataTable[i,2]){
      res<-dataTable[i,3]
    }
  }
  return(as.character(res))
  }

这将检查以确保包含这些值，但有更简单的方法可以做到这一点。对return行的修改使R不会列出因子水平。

作为参考，这将利用R中的矢量化：

sheldon_game<-function(A, B) {
    Avals <- unique(dataTable[, 1])
    Bvals <- unique(dataTable[, 2])
    if(A %in% Avals & B %in% Bvals) {
        idx <- which(A==dataTable[, 1] & B==dataTable[, 2])
        return(as.character(dataTable[idx, 3]))
    } else return("Parameters out of bound!")
}