R语言如何编写循环输出每个月份对应的天数

问题原因 #

你使用的嵌套for循环会让每一个月份依次匹配全部12个天数，最终输出12*12=144条重复结果，不符合两个向量一一对应的需求。

修改要点 #

• months和days两个向量长度均为12，内容一一对应，不需要嵌套循环，仅通过单循环遍历索引，同时取出对应位置的月份和天数即可
• 原代码中月份拼写有误：Februari需修正为February，才能和预期输出内容一致
• 要输出带[1] "内容"的R标准打印格式，直接使用print()搭配字符串拼接函数paste()即可，不需要手动用cat()拼接格式

修正后代码 #

循环写法 #

days <- c("31","29","31","30","31","30","31","31","30","31","30","31")
# 修正月份拼写错误
months <- c("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")

# 单循环遍历索引，匹配对应月份和天数
for (i in seq_along(months)) {
  print(paste(months[i], "has", days[i], "days"))
}

更简洁的向量化写法（无需显式循环，符合R语言使用习惯） #

days <- c("31","29","31","30","31","30","31","31","30","31","30","31")
months <- c("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December")

print(paste(months, "has", days, "days"))

以上两种写法运行后均可得到你需要的12条目标输出。

内容的提问来源于stack exchange，提问作者Helan.ge