Question

好的所以我正在编写这个循环，我打算循环并将我的矢量名称粘贴到循环中。粘贴变量名称的目标目标是在URL链接中，以及在“”标记之间的destfile名称。

到目前为止，这是我的程序：

    # Download ETF AUM Files 
    file.list <- c("DDM","MVV","QLD","SAA","SSO","TQQQ","UDOW","UMDD","UPRO","URTY","UWM", "BIB", "FINU","LTL","ROM", "RXL", "SVXY","UBIO","UCC","UGE","UPW","URE","USD","UXI","UYG","UYM","DOG","DXD","MYY","MZZ","PSQ","QID","RWM","SBB","SDD","SDOW","SDS","SH","SPXU","SQQQ","SRTY","TWM","SMDD","UVXY","VIXM","VIXY")


    # Loop 
     for (f in 1:length(file.list)) {
        next.file <- file.list[i]
        file.name.variable <- paste(next.file[1])
        url <- "https://accounts.profunds.com/etfdata/ByFund/file.name.variable-historical_nav.csv"
        destfile <- "C:/R Projects/Data/etf_aum/file.name.variable.csv"
        download.file(url, destfile, mode="wb")
}

正如你所看到的...我希望在向量中输入变量的名称并粘贴到我的字符串中以获取url和destfile ...有什么办法可以做到这一点吗？

现在它不会认识到我希望这个名字是一个变量，因为它已经在“”中标记它会把它作为它的书写。

Answer 1

这似乎就是你所追求的。

for (i in 1 : length(file.list)) {
  file.name.variable <-  file.list[i]

  url <- paste0("https://accounts.profunds.com/etfdata/ByFund/", 
                   file.name.variable, "-historical_nav.csv")

  destfile <- paste0("C:/R Projects/Data/etf_aum/",
                          file.name.variable, "csv")

  download.file(url, destfile, mode="wb")
}

在“”字符串中插入变量

1 个答案: