创建一个空的 data.frame [英] Create an empty data.frame

问题描述

我正在尝试初始化一个没有任何行的 data.frame.基本上，我想为每一列指定数据类型并命名它们，但不会因此创建任何行.

I'm trying to initialize a data.frame without any rows. Basically, I want to specify the data types for each column and name them, but not have any rows created as a result.

到目前为止我能做的最好的是:

The best I've been able to do so far is something like:

df <- data.frame(Date=as.Date("01/01/2000", format="%m/%d/%Y"), 
                 File="", User="", stringsAsFactors=FALSE)
df <- df[-1,]

它创建了一个 data.frame，其中一行包含我想要的所有数据类型和列名，但也创建了一个无用的行，然后需要将其删除.

Which creates a data.frame with a single row containing all of the data types and column names I wanted, but also creates a useless row which then needs to be removed.

有没有更好的方法来做到这一点?

Is there a better way to do this?

推荐答案

用空向量初始化即可:

df <- data.frame(Date=as.Date(character()),
                 File=character(), 
                 User=character(), 
                 stringsAsFactors=FALSE) 

<小时>

这是另一个具有不同列类型的示例:

---

Here's an other example with different column types :

df <- data.frame(Doubles=double(),
                 Ints=integer(),
                 Factors=factor(),
                 Logicals=logical(),
                 Characters=character(),
                 stringsAsFactors=FALSE)

str(df)
> str(df)
'data.frame':   0 obs. of  5 variables:
 $ Doubles   : num 
 $ Ints      : int 
 $ Factors   : Factor w/ 0 levels: 
 $ Logicals  : logi 
 $ Characters: chr 

注意:

使用错误类型的空列初始化 data.frame 不会阻止进一步添加具有不同类型列的行.
这种方法有点更安全，因为您将从一开始就拥有正确的列类型，因此如果您的代码依赖于某些列类型检查，它甚至可以使用 data.frame 零行.

Initializing a data.frame with an empty column of the wrong type does not prevent further additions of rows having columns of different types.
This method is just a bit safer in the sense that you'll have the correct column types from the beginning, hence if your code relies on some column type checking, it will work even with a data.frame with zero rows.

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