将空列添加到具有向量中指定名称的数据框 [英] Add empty columns to a dataframe with specified names from a vector

问题描述

我有一个数据框，df，已经有许多数据列.我有一个充满字符串的向量 namevector.我需要使用 namevector 中的列名称将空列添加到 df.

I have a dataframe, df, with a a number of columns of data already. I have a vector, namevector, full of strings. I need empty columns added to df with the names of the columns from namevector.

我正在尝试使用此 for 循环添加列，迭代 namevector 中的每个字符串.

I am trying to add columns with this for loop, iterating over each string in namevector.

for (i in length(namevector)) {
  df[, i] <- NA
}

但我留下了这个错误:

[<-.data.frame(*tmp*, , i, value = NA) 中的错误:新列会在现有列之后留下孔

Error in [<-.data.frame(*tmp*, , i, value = NA) : new columns would leave holes after existing columns

或者，我想用正确的名称创建一个空的数据框，然后 cbind 将两个数据框连接在一起，但我不知道如何进行编码.

Alternatively, I have thought of creating an empty dataframe with the correct names, then cbind-ing the two dataframes together but am not sure how to go about coding this.

我将如何解决这个问题?

How would I go about resolving this?

推荐答案

问题与您的代码有关:

for(i in length(namevector))

你需要问问自己:什么是length(namevector)?这是一个数字.所以基本上你是说:

You need to ask yourself: what is length(namevector)? It's one number. So essentially you're saying:

for(i in 11)
df[,i] <- NA

或者更简单:

df[,11] <- NA

这就是您收到错误的原因.你想要的是:

That's why you're getting an error. What you want is:

for(i in namevector)
    df[,i] <- NA

或者更简单:

df[,namevector] <- NA

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