拆分数据帧以传递到R中的sprintf [英] Split Data Frame for passing to sprintf in R

问题描述

我有一个sprintf格式的字符串，试图通过它解析R中的数据帧。我构建了此代码来做到这一点，但是如果不难看的话也算什么。有什么更好的方法？

I have a sprintf format string that I'm trying to parse a dataframe in R through. I built this code to do it, but it is nothing if not ugly. What's a better way to do this?

writeData<-function(DataSet,FirstLine,FmtString,fName){
    correctLine<-function (MyLine,FmtString){
        do.call(sprintf,c(FmtString,MyLine))
    }
    #why the ugly split code? Because otherwise it casts my nice data frame as characters which confuses sprintf.
    outLines=lapply(split(DataSet,1:NROW(DataSet)),function (x){correctLine(x,FmtString)})
    writeLines(unlist(outLines),fName)
    return(0)
}

这里有一个例子：

z=data.frame(d1=c("A","B","C"),d2=c(1,2,3),d3=c("D","E","F"),stringsAsFactors=FALSE)
fmt="%s %0.3f %s"
writeData(z,"",fmt,"~/sample.txt")

对比度：

correctLine<-function (MyLine,FmtString){do.call(sprintf,c(FmtString,MyLine))}
apply(z,1,function(x) {correctLine(x,fmt)}) #Errors out, wants a list
correctLine<-function (MyLine,FmtString){do.call(sprintf,as.list(c(FmtString,MyLine)))}
apply(z,1,function(x) {correctLine(x,fmt)}) # - still unhappy, now we have a character array. This is the problem.

推荐答案

如果我了解您要正确执行的操作，您实际上只需要对所有列调用 sprintf 一次即可进行格式化。例如

If I understand what you are trying to do correctly, you really only need to call sprintf once with all your columns to do the formatting. For example

writeData <- function(DataSet,FirstLine, FmtString,fName){
    outlines <- do.call("sprintf", c(FmtString, DataSet))
    writeLines(outLines,fName)
    return(0)
}

R中的大多数函数都旨在与数据向量一起使用，因此一次只传递整个列，而不是遍历行。

Most functions in R are meant to work with vectors of data so just pass in the entire column at a time rather than iterating over the rows.

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