在R data.frame中，将行名提升为实际列 [英] In R data.frame, promote rownames to actual column

问题描述

我有一个具有这样的列和行名称的数据框，

I have a data frame with one column and row names like this,

 > df
             freq
    hello     4
    sorry     2
    bad       9
    good      4     
    great     1

我想将其更改为以下两列并更改行名，

I want to change that to two columns as below and change row names,

 > df
         word   freq
    1    hello   4
    2    sorry   2
    3    bad     9
    4    good    4
    5    great   1

推荐答案

df <- data.frame(freq=c(4,2,9,4,1),row.names=c('hello','sorry','bad','good','great'));
df;
##       freq
## hello    4
## sorry    2
## bad      9
## good     4
## great    1
df <- data.frame(word=rownames(df),freq=df$freq);
df;
##    word freq
## 1 hello    4
## 2 sorry    2
## 3   bad    9
## 4  good    4
## 5 great    1

---

编辑：再三考虑，一种更好的方法是避免对现有列的名称进行硬编码，并且可以与任意数量的现有列一起使用，如下所示：

---

On second thought, a better way to do this, which avoids having to hard-code the name of the existing column, and will work with any number of existing columns, is as follows:

df <- data.frame(word=rownames(df),df,row.names=NULL);
df;
##    word freq
## 1 hello    4
## 2 sorry    2
## 3   bad    9
## 4  good    4
## 5 great    1

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