在 for 循环中将数据帧附加在一起 [英] Append data frames together in a for loop

问题描述

我有一个 for 循环，它在每次迭代后生成一个数据帧.我想将所有数据框附加在一起，但发现这很困难.以下是我我正在尝试，请建议如何修复它:

I have a for loop which produces a data frame after each iteration. I want to append all data frames together but finding it difficult. Following is what I am trying, please suggest how to fix it:

d = NULL
for (i in 1:7) {

  # vector output
  model <- #some processing

  # add vector to a dataframe
  df <- data.frame(model)

}

df_total <- rbind(d,df)

推荐答案

不要在循环内进行.制作一个列表，然后在循环之外将它们组合起来.

Don't do it inside the loop. Make a list, then combine them outside the loop.

datalist = list()

for (i in 1:5) {
    # ... make some data
    dat <- data.frame(x = rnorm(10), y = runif(10))
    dat$i <- i  # maybe you want to keep track of which iteration produced it?
    datalist[[i]] <- dat # add it to your list
}

big_data = do.call(rbind, datalist)
# or big_data <- dplyr::bind_rows(datalist)
# or big_data <- data.table::rbindlist(datalist)

这是一种更像 R 的做事方式.它也可以显着更快，特别是如果您使用 dplyr::bind_rows 或 data.table::rbindlist 进行数据帧的最终组合.

This is a much more R-like way to do things. It can also be substantially faster, especially if you use dplyr::bind_rows or data.table::rbindlist for the final combining of data frames.

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