R：使用函数将新列添加到数据框 [英] R: Add new column to dataframe using function

问题描述

我有一个数据框 df ，它有两列，术语和频率。我还有一个包含存储在一个向量索引的向量中的给定ID的术语列表。为了说明这两个信息，我有以下内容：

I have a data frame df that has two columns, term and frequency. I also have a list of terms with given IDs stored in a vector called indices. To illustrate these two info, I have the following:

> head(indices)
   Term
1    hello
256  i
33   the

另外，对于数据框。

> head(df)
   Term  Freq
1  i     24
2  hello 12
3  the   28

我想在 df 中添加一个名为 TermID 的列，这只是矢量索引中的术语索引。我试过使用 dplyr :: mutate ，但无效。以下是我的代码

I want to add a column in df called TermID which will just be the index of the term in the vector indices. I have tried using dplyr::mutate but to no avail. Here is my code below

library(dplyr)

whichindex <- function(term){
              ind <- which(indices == as.character(term))
              ind}

mutate(df, TermID = whichindex(Term))

我得到的输出是一个 df ，它有一个新的列 TermID ，但 TermID 的所有值都相同。

What I am getting as output is a df that has a new column called TermID, but all the values for TermID are the same.

有人可以帮我弄清楚我做错了什么吗？如果您可以在[R]中推荐更有效的算法来执行此操作，那么这也是很好的。我已经在Python中实现了这一点，我没有遇到这样的问题。

Can someone help me figure out what I am doing wrong? It would be nice as well if you can recommend a more efficient algorithm to do this in [R]. I have implemented this in Python and I have not encountered such issues.

提前感谢

推荐答案

如何？

df %>% rowwise() %>% mutate(TermID = grep(Term,indices))

w /示例数据：

library(dplyr)
indices <- c("hello","i","the")
df <- data_frame(Term = c("i","hello","the"), Freq = c(24,12,28))

df_res <- df %>% rowwise() %>% mutate(TermID = grep(Term,indices))
df_res

：

Source: local data frame [3 x 3]
Groups: <by row>

   Term Freq TermID
1     i   24      2
2 hello   12      1
3   the   28      3

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