连接列并将其添加到Data Frame的开头 [英] Concatenate columns and add them to beginning of Data Frame

问题描述

Noob这里到R.试图弄清楚一些东西。我需要构建一个向数据集开始添加新列的函数。这个新列是用户指定的其他列中的值的连接。

Noob here to R. Trying to figure something out. I need to build a function that adds a new column to the beginning of a dataset. This new column is a concatenation of the values in other columns that the user specifies.

想象一下，这是名为myDataSet的数据集：

Imagine this is the data set named myDataSet:

col_1    col_2    col_3    col_4
bat      red      1        a
cow      orange   2        b
dog      green    3        c

用户可以使用如下功能：

The user could use the function like so:

addPrimaryKey(myDataSet, cols=c(1,3,4))

得到一个新的数据集的结果，列1,3和4连接成一个名为ID的列，并添加到开头，如下所示：

to get the result of a new data set with columns 1, 3 and 4 concatenated into a column called ID and added to the beginning, like so:

ID        col_1    col_2    col_3    col_4
bat1a     bat      red      1        a
cow2b     cow      orange   2        b
dog4c     dog      green    3        c

这是我一直在努力的脚本，但是我一直在盯着它，我想我犯了一些错误。我不知道如何将参数中的列号从粘贴函数中正确地获取。

This is the script I have been working on but I have been staring at it so long, I think I have made a few mistakes. I can't figure out how to get the column numbers from the arguments into the paste function properly.

addPrimaryKey <- function(df, cols=NULL){

  newVector = rep(NA, length(cols)) ##initialize vector to length of columns

  colsN <- as.numeric(cols)

  df <- cbind(ID=paste(
    for(i in 1:length(colsN)){
      holder <- df[colsN[i]]
      holder
    }
  , sep=""), df) ##concatenate the selected columns and add as ID column to df
df
}

任何帮助将不胜感激。非常感谢

Any help would be greatly appreciated. Thanks so much

推荐答案

paste0 code> do.call ：

paste0 works fine, with some help from do.call:

do.call(paste0, mydf[c(1, 3, 4)])
# [1] "bat1a" "cow2b" "dog3c"

因此，您的函数可以是：

Your function, thus, can be something like:

addPrimaryKey <- function(inDF, cols) {
  cbind(ID = do.call(paste0, inDF[cols]),
        inDF)
}

您可能还想查看交互：

interaction(mydf[c(1, 3, 4)], drop=TRUE)
# [1] bat.1.a cow.2.b dog.3.c
# Levels: bat.1.a cow.2.b dog.3.c

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