如何强制列表对象键入“ double”

密码:

a <- structure(list(`X$Days` = c("10", "38", "66", "101", "129", "185", "283",
"374")), .Names = "X$Days")

那么 a就像

$`X$Days`
[1] "10"  "38"  "66"  "101" "129" "185" "283" "374"

我想强制 a数组的数值，但强制函数返回我

Error: (list) object cannot be coerced to type 'double'

谢谢,

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最佳答案

If you want to convert all elements of a to a single numeric vector and length(a) is greater than 1 (OK, even if it is of length 1), you could unlist the object first and then convert.

as.numeric(unlist(a))
# [1]  10  38  66 101 129 185 283 374

Bear in mind that there aren't any quality controls here. Also, X$Days a mighty odd name.

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If your list as multiple elements that need to be converted to numeric, you can achieve this with lapply(a, as.numeric).

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You can also use list subsetting to select the element you want to convert. It would be useful if your list had more than 1 element.

as.numeric(a[[1]])

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There are problems with some data. Consider:

as.double(as.character("2.e")) # This results in 2

Another solution:

get_numbers <- function(X) {
X[toupper(X) != tolower(X)] <- NA
return(as.double(as.character(X)))
}

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In this case a loop will also do the job (and is usually sufficiently fast).

a <- array(0, dim=dim(X))
for (i in 1:ncol(X)) {a[,i] <- X[,i]}