Rock, Paper, Scissors, Lizard, Spock游戏R语言sheldon_game函数参数校验异常问题求助

Let's break down why your current function throws errors even with valid inputs, then fix it step by step.

The Root Problem #

Your sheldon_game function's loop logic is flawed:

• For every row in dataTable, if the current row's Player-1 and Player-2 don't match your input A and B, it immediately calls stop().
• That means even if there's a valid matching row later in the table, the loop hits a non-matching row first and crashes before finding the correct entry.

The Fix #

We'll restructure the function to first validate inputs, then fetch the outcome efficiently without a problematic loop:

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){
  # Define valid moves first
  valid_moves <- c("Rock", "Paper", "Scissors", "Lizard", "Spock")
  
  # Step 1: Validate inputs are in valid moves
  if (!A %in% valid_moves || !B %in% valid_moves) {
    stop("Parameters out of bounds! Valid moves are: Rock, Paper, Scissors, Lizard, Spock")
  }
  
  # Step 2: Find the matching row and return outcome
  match_row <- dataTable[dataTable$`Player-1` == A & dataTable$`Player-2` == B, ]
  res <- match_row$Outcome
  
  return(res)
}

# Test valid input
sheldon_game("Scissors","Paper")  # Should return "Player 1 Wins!"

# Test invalid input
sheldon_game("Scissors","Banana") # Should throw error

Key Improvements #

• Explicit Input Validation: We first check if A and B are in the list of valid moves. This catches invalid inputs immediately, before even looking at the outcome table.
• Efficient Outcome Lookup: Instead of looping through every row, we use R's vectorized subsetting to directly find the row where both Player-1 and Player-2 match the inputs. This is faster and avoids the loop logic error.
• Clearer Error Message: The error message now explicitly lists valid moves to help users correct their input.

内容的提问来源于stack exchange，提问作者Iftikhar