是否有可能追加到已有的文件的第一行？ [英] Is it possible to append to the first line of an exisiting file?

问题描述

我已经看了几个有能力将文本添加到现有的数据文件中的函数（.csv或.txt），如write.table，write.lines或下沉。

I've looked at several of the functions that are able to add text to an existing data file (.csv or .txt) such as write.table, write.lines, or sink.

在追加参数= TRUE，新的数据总是在文件的最后既有线后加入。是否有可能将数据添加到第一行的现有文件（一个标题下） - AKA相反的追加

When the append argument =TRUE, the new data is always added after the last existing line of the file. Is it possible to add data to an existing file on first line (below a header)- AKA opposite of append?

如果有一个数据帧：

DF <- as.data.frame(matrix(seq(20),nrow=5,ncol=4))
colnames(DF) <- c("A", "B", "C", "D")
write.table(DF, "DF.csv", row.names=FALSE, sep=",")

我可以追加新的数据帧像这样的最后一行

I can append a new data frame to the last line like this

A <- 1
A <- data.frame(A)
A$B <- 1
A$C <- 1
A$D <- 1
write.table(A, "DF.csv", row.names=FALSE, sep=",", append=TRUE, col.names=FALSE)

这是接近我想要的。但我真的很想有上述行添加到DF.csv（右头下面）的第一行，像这样

Which is close to what I want. But I would really like to have the above line to be added to the first line of the DF.csv (right below the header) like so

A   B   C   D
1   1   1   1
1   6   11  16
2   7   12  17
3   8   13  18
4   9   14  19
5   10  15  20

需要明确的是，我不希望增加一行到中河数据帧我希望能行添加到文件的开头第r环境之外。正如追加可用于将数据添加到一个外部.csv文件的最后，我希望能数据追加到.csv文件的开头，让自己的最新数据始终排在第一位登场（以避免通过一个长文件的结尾滚动以查看最新的数据）。

To be clear, I'd not looking to add a row into a data frame within R. I am hoping to add a row to the beginning of a file outside of the R environment. Just as append can be used to add data to the end of an external .csv file, I am hoping to "append" data to the beginning of a .csv file, so that my latest data always comes up in the first row (to avoid scrolling through to the end of a long file to see the most current data).

推荐答案

编写您自己的功能：

my.write.table <- function(df, filename, sep)
{
   ## read the existing content
   temp.df <- read.table(filename, sep)

   ## append in front
   df <- rbind(df, temp.df)

   ## write back the whole data frame
   write.table(df, filename, sep)
}

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