使用程序將類更改爲自定義類

Question

使用程序包openxlsx準備將數據框寫入Excel工作簿，我能夠使用列/列方式運行openxlsx's vignette中的示例以更改變量的class。

## data.frame to write 
df <- data.frame("Date" = Sys.Date()-0:4, 
"Logical" = c(TRUE, FALSE, TRUE, TRUE, FALSE), 
"Currency" = paste("$",-2:2), 
"Accounting" = -2:2, 
"hLink" = "http://cran.r-project.org/", 
"Percentage" = seq(-1, 1, length.out=5), 
"TinyNumber" = runif(5)/1E9, stringsAsFactors = FALSE) 

## Below comes the custom class assignation used for excel formatting 
class(df$Currency) <- "currency" 
class(df$Accounting) <- "accounting" 
class(df$hLink)  <- "hyperlink" 
class(df$Percentage) <- "percentage" 
class(df$TinyNumber) <- "scientific" 

## Works ! 
class(df$Percentage) 
[1] "percentage" 

爲了我自己的數據集工作，我想用dplyr更改類列，其名稱匹配給定的字符串（如下）。

我試過到目前爲止：

require(tidyverse) 
fn_toPercentage <- function(x){class(x)<-"percentage"} 

df2 <- df %>% 
    mutate_at(vars(starts_with("Percent")),funs(fn_toPercentage)) 

## Check: 
lapply(df2,class) 
$Date 
[1] "Date" 

$Logical 
[1] "logical" 

$Currency 
[1] "character" 

$Accounting 
[1] "integer" 

$hLink 
[1] "character" 

## Failed !  
$Percentage 
[1] "character" 

$TinyNumber 
[1] "numeric" 

我有一種感覺，功能setAs可能是有關我的問題，但我無法弄清楚如何使用它。

感謝您的幫助

Answer 1

貌似存在fn_toPercentage錯誤。它應該看起來像這樣：

fn_toPercentage <- function(x){ 
    class(x)<-"percentage" 
    x 
}