如何将某些列仅转换为数字？ [英] How to convert certain columns only to numeric?

问题描述

如何仅将数据框中的某些列转换为数字？

How can I convert certain columns only in a data frame to numeric?

例如，我有以下数据框：

For instance, I have this data frame:

structure(list(airport = c("EGLL", "EGLL"), xdate = c("2016-07-28", 
"2016-07-31"), ws = c("6", "5"), wd = c("237", "299"), humidity = c("68", 
"55")), .Names = c("airport", "xdate", "ws", "wd", "humidity"
), row.names = 1:2, class = "data.frame")

我只想转换 ws ， wd 和湿度转换为数字，不 机场和xdate 。

I just want to convert ws, wd, and humidity to numeric, not airport and xdate.

如果我这样做：

columns <- sapply(weatherDF, is.character)
weatherDF[, columns] <- lapply(weatherDF[, columns, drop = FALSE], function(x) as.numeric(as.character(x)))

我正在转换机场和 xdate 转换为数字，然后收到此警告：

I am converting airport and xdate to numberic, and then I get this warning:

Warning messages:
1: In FUN(X[[i]], ...) : NAs introduced by coercion
2: In FUN(X[[i]], ...) : NAs introduced by coercion

引入

现在我的数据框变为：

And now my data frame has become:

structure(list(airport = c(NA_real_, NA_real_), xdate = c(NA_real_, 
NA_real_), ws = c(6, 5), wd = c(237, 299), humidity = c(68, 55
)), .Names = c("airport", "xdate", "ws", "wd", "humidity"), row.names = 1:2, class = "data.frame")

任何想法如何将它们转换

Any ideas how I can convert them properly?

推荐答案

1）您所有的列是字符
列<-sapply（weatherDF，is.character）

airport    xdate       ws       wd humidity 
    TRUE     TRUE     TRUE     TRUE     TRUE

2）为什么不简单？

weatherDF [，3：ncol（weatherDF）]<-lapply（3： ncol（weatherDF），函数（x）as.numeric（we atherDF [[x]]））

或

columns <-c("ws", "wd", "humidity")
weatherDF[, columns] <- lapply(columns, function(x) as.numeric(weatherDF[[x]]))

如果您不知道哪几列是数字，则可以尝试使用 tryCatch
like

If your dont know which columns is numeric you can try to find it using tryCatch like

weatherDF[,1:ncol(weatherDF)]=lapply(1:ncol(weatherDF),function(x) {
  tryCatch({
    as.numeric(weatherDF[[x]])
    },warning = function(w) {
    weatherDF[[x]]}
        )} )

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