如何防止将数据框列分类为字符而不是数字 [英] how to prevent dataframe columns being classed as character instead of numeric

问题描述

早上好。

我正骑自行车穿过一些数据，在我走的时候建立一个数据框。每次添加或替换数据帧中的一行时，数值将被归类为字符，我必须重新分类。我假设在将数据添加到数据框中时，我做错了什么？

I am cycling through some data, building a dataframe as I go. Every time I add or replace a row in the dataframe, numeric values get classed as character, and I have to re-class them. I assume I am doing something wrong when adding the data to the dataframe ?

test.df<-data.frame(SIDE=rep("",5),n=rep(NA, 5),c1=rep(NA,5),stringsAsFactors=FALSE)
test.df[1,]<-cbind("A",1,256)
test.df[2,]<-cbind("A",2,258)
test.df[3,]<-cbind("A",3,350)
test.df[4,]<-cbind("A",4,400)
test.df[5,]<-cbind("A",5,360)
summary(test.df)
 SIDE                n                  c1           
  Length:5           Length:5           Length:5          
  Class :character   Class :character   Class :character  
  Mode  :character   Mode  :character   Mode  :character  

将数字列转换为数字：

test.df[, c(2:3)] <- sapply(test.df[, c(2:3)], as.numeric)
summary(test.df)
 SIDE                 n           c1       
 Length:5           Min.   :1   Min.   :256.0  
 Class :character   1st Qu.:2   1st Qu.:258.0  
 Mode  :character   Median :3   Median :350.0  
                    Mean   :3   Mean   :324.8  
                    3rd Qu.:4   3rd Qu.:360.0  
                    Max.   :5   Max.   :400.0  

所以数据框现在是我预期的 - 1列字符数据和2个数字。但是，如果我再次更改一个行：

So the dataframe is now as I expect it - 1 column of character data and 2 of numeric. However if I change one of the rows again:

test.df[5,]<-cbind("A",5,360)
summary(test.df)
 SIDE                n                  c1           
 Length:5           Length:5           Length:5          
 Class :character   Class :character   Class :character  
 Mode  :character   Mode  :character   Mode  :character  

它已经回到所有角色！

有没有办法确保在数据框中附加/更改数据时保留适当的类？

Is there any way to ensure that when I append/change data in the dataframe that it keeps the appropriate classes ?

谢谢， Pete

推荐答案

cbind（A，5,360） ，它只能保存一种类型，即您的案例中的字符。

cbind("A",5,360) is a matrix, which can hold only one type, i.e. character in your case.

使用data.frame方法：

Use the data.frame method:

cbind.data.frame("A",5,360)

然而，骑自行车通过一些数据可能是在R中执行此操作的最不有效的方法。

However, "cycling through some data" is probably the least efficient way to do this in R.

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