R中使用mutate调用自定义函数时vapply报错的解决咨询

问题分析 #

当前的win_percent函数是为单个球队和单个日期设计的，但在mutate中调用时，传递的是整个Tm列和DateFull列（长度为2684的向量），函数内部处理后返回的结果长度与mutate期望的每行对应单个值的要求不匹配，因此触发错误。

另外原函数存在两处可优化点：

• 球队名称替换使用大量重复赋值，代码冗余
• 每行调用一次mlb_standings，API请求次数过多，效率极低

修复方案 #

方案1：逐行处理（快速修改） #

使用rowwise()让mutate逐行传递单个值给函数，同时用recode简化球队名称映射逻辑：

library(baseballr)
library(tidyverse)

win_percent <- function(Tm, DateFull) {
  # 合并两个联盟的 standings 数据
  df <- rbind(mlb_standings(season = 2022, date = DateFull, league_id = 104),
              mlb_standings(season = 2022, date = DateFull, league_id = 103))
  
  # 用recode简化球队全称到缩写的映射
  df <- df %>%
    mutate(team_records_team_name = recode(team_records_team_name,
      "Baltimore Orioles" = "BAL",
      "Boston Red Sox" = "BOS",
      "Chicago White Sox" = "CHW",
      "Cleveland Guardians" = "CLE",
      "Detroit Tigers" = "DET",
      "Houston Astros" = "HOU",
      "Kansas City Royals" = "KCR",
      "Los Angeles Angels" = "LAA",
      "Minnesota Twins" = "MIN",
      "New York Yankees" = "NYY",
      "Oakland Athletics" = "OAK",
      "Seattle Mariners" = "SEA",
      "Tampa Bay Rays" = "TBR",
      "Texas Rangers" = "TEX",
      "Toronto Blue Jays" = "TOR",
      "Arizona Diamondbacks" = "ARI",
      "Atlanta Braves" = "ATL",
      "Chicago Cubs" = "CHC",
      "Cincinnati Reds" = "CIN",
      "Colorado Rockies" = "COL",
      "Los Angeles Dodgers" = "LAD",
      "Miami Marlins" = "MIA",
      "Milwaukee Brewers" = "MIL",
      "New York Mets" = "NYM",
      "Philadelphia Phillies" = "PHI",
      "Pittsburgh Pirates" = "PIT",
      "San Diego Padres" = "SDP",
      "San Francisco Giants" = "SFG",
      "St. Louis Cardinals" = "STL",
      "Washington Nationals" = "WSN"
    ))
  
  # 筛选目标球队并提取胜率
  df %>%
    filter(team_records_team_name == Tm) %>%
    pull(team_records_winning_percentage) %>%
    as.numeric()
}

# 调用时添加rowwise()实现逐行处理
df %>%
  rowwise() %>%
  mutate(win_perc = win_percent(Tm, DateFull)) %>%
  ungroup() # 处理完成后取消逐行模式

方案2：向量化处理（高效推荐） #

避免重复调用API，先获取所有唯一日期的standings数据，再与原数据框关联，大幅提升效率：

library(baseballr)
library(tidyverse)

# 1. 获取所有唯一日期的standings数据
unique_dates <- unique(df$DateFull)
standings_list <- map(unique_dates, function(date) {
  rbind(mlb_standings(season = 2022, date = date, league_id = 104),
        mlb_standings(season = 2022, date = date, league_id = 103)) %>%
    mutate(DateFull = date) %>%
    # 球队全称转缩写
    mutate(team_records_team_name = recode(team_records_team_name,
      "Baltimore Orioles" = "BAL",
      "Boston Red Sox" = "BOS",
      "Chicago White Sox" = "CHW",
      "Cleveland Guardians" = "CLE",
      "Detroit Tigers" = "DET",
      "Houston Astros" = "HOU",
      "Kansas City Royals" = "KCR",
      "Los Angeles Angels" = "LAA",
      "Minnesota Twins" = "MIN",
      "New York Yankees" = "NYY",
      "Oakland Athletics" = "OAK",
      "Seattle Mariners" = "SEA",
      "Tampa Bay Rays" = "TBR",
      "Texas Rangers" = "TEX",
      "Toronto Blue Jays" = "TOR",
      "Arizona Diamondbacks" = "ARI",
      "Atlanta Braves" = "ATL",
      "Chicago Cubs" = "CHC",
      "Cincinnati Reds" = "CIN",
      "Colorado Rockies" = "COL",
      "Los Angeles Dodgers" = "LAD",
      "Miami Marlins" = "MIA",
      "Milwaukee Brewers" = "MIL",
      "New York Mets" = "NYM",
      "Philadelphia Phillies" = "PHI",
      "Pittsburgh Pirates" = "PIT",
      "San Diego Padres" = "SDP",
      "San Francisco Giants" = "SFG",
      "St. Louis Cardinals" = "STL",
      "Washington Nationals" = "WSN"
    )) %>%
    select(DateFull, Tm = team_records_team_name, win_perc = team_records_winning_percentage) %>%
    mutate(win_perc = as.numeric(win_perc))
})

# 合并所有日期的standings数据
standings_df <- bind_rows(standings_list)

# 2. 与原数据框关联，获取对应球队当日胜率
df_with_winperc <- df %>%
  left_join(standings_df, by = c("Tm", "DateFull"))

错误原因详解 #

mutate默认是向量化操作，会将整个列（向量）传递给函数。原函数中，当DateFull是长度2684的向量时，mlb_standings会被调用2684次，后续的filter和select逻辑在处理向量时出现长度不匹配，导致mutate无法将结果正确映射到每行数据，最终触发报错。

内容的提问来源于stack exchange，提问作者mjc0203