我在下面有一个数据帧。
asd <- data.frame(a=c(1:10),b=c(11,20),c=(21:30),d=c(31:40),e=c(41,50),f=c(51,60))
以下是包含 asd 列名称的 2 个向量
Column_list1 <- c("a","b","d")
Column_list2 <- c("c","e","f")
以下是必填列列表
mandatory_column <- c("a","b","d","e")
现在实际上我的问题是当我尝试运行asd[Column_list1]
时,结果应该抛出一条消息。因为必填列应该c("a","b","d","e")
,而且Column_list1
没有"e",我需要打印消息,"请包括"e"列"。这是有可能实现的吗?
预期产出
asd[Column_list1]
Please include column "e" as well
asd[mandatory_column]
a b d e
1 1 11 31 41
2 2 20 32 50
3 3 11 33 41
4 4 20 34 50
5 5 11 35 41
6 6 20 36 50
7 7 11 37 41
8 8 20 38 50
9 9 11 39 41
10 10 20 40 50
如果你想弄乱你的对象asd
的类,就会想到一个S3方法。
`[.special` <- function(x, i, ..., mandatory = mandatory_column){
on.exit({
cols_missing <- setdiff(mandatory, i)
if(length(cols_missing) > 0){
msg <- paste(sQuote(cols_missing), collapse = ", ")
msg <- paste("Please include columns", msg)
warning(msg)
}
})
NextMethod(x, i, ...)
}
Column_list1 <- c("a","b","d")
Column_list2 <- c("c","e","f")
mandatory_column <- c("a","b","d","e")
第一次调用仍调用[.data.frame
方法。
asd[Column_list1]
现在调用[.special
方法。它对数据进行子集化并发出警告。
class(asd) <- c("special", class(asd))
asd[Column_list1]
asd[Column_list2]
asd[mandatory_column]
mandatory_columns <- c("cyl", "disp", "gear", "quux")
stopifnot(all(mandatory_columns %in% colnames(mtcars)))
# Error: all(mandatory_columns %in% colnames(mtcars)) is not TRUE
或者:
missingfields <- setdiff(mandatory_columns, colnames(mtcars))
if (length(missingfields)) {
stop("missing fields: ", paste(sQuote(missingfields), collapse = ", "))
}
# Error: missing fields: 'quux'
### with a subset of mtcars, demonstrating more missing columns:
missingfields <- setdiff(mandatory_columns, colnames(mtcars)[1:4])
if (length(missingfields)) {
stop("missing fields: ", paste(sQuote(missingfields), collapse = ", "))
}
# Error: missing fields: 'gear', 'quux'
如果您使用的是shiny
并希望在不停止程序的情况下进行验证/消息,请使用validate
、need
和req
:
output$my_table <- renderTable({
validate(need(req(all(mandatory_columns %in% names(mtcars))), "Missing columns"))
asd[,mandatory_columns]
})