dplyr group_by可变长度限制

Question

我遇到了一些问题，dplyr返回错误“index out of bounds”。

似乎只有长变量名才会发生。显然，这可以通过重命名有问题的变量来解决，但我想把它放在这里，以帮助其他人解决相同的问题，因为返回的错误不提供信息。

> test <- data.frame(name = rep(c("orange", "pear", "apple", "bear"), 2) , 
+                    value = rnorm(8), stringsAsFactors = FALSE)
> 
> group_by(test, name) %>% summarise(mean(value))
Source: local data frame [4 x 2]

    name mean(value)
1  apple -0.34881128
2   bear  1.01526013
3 orange -0.68778455
4   pear -0.06635953
> 
> test$reallyreallyreallyreallyreallylongvarname <- test$name
> group_by(test, reallyreallyreallyreallyreallylongvarname) %>% summarise(mean(value))
Error in eval(expr, envir, enclos) : index out of bounds

Answer 1

可能的解决方法是在quote()内使用group_by()。

> group_by(test, quote(reallyreallyreallyreallyreallylongvarname)) %>% summarise(mean(value))
Source: local data frame [4 x 2]

  quote(reallyreallyreallyreallyreallyl... mean(value)
1                                    apple -0.34881128
2                                     bear  1.01526013
3                                   orange -0.68778455
4                                     pear -0.06635953