如何在 R 中循环数据集并以 PDF/EXCEL 格式单独提取每个值

Question

我有一个数据集，其中包含 ID 列和要下载的 URL 列，每个 ID 有 2 个 URL， 我想下载每两个 URL 并将它们转换为一个以其 ID 命名的 PDF 文件。 我想要每个 ID 一份 PDF。

# demo dataset

df <- data.frame(ID = c(1,1,2,2,3,3),
                 Full_Path = c("https://test1.png","https://test1.png",
                               "https://test1.png","https://test1.png",
                               "https://test1.png","https://test1.png"))

for (url in df$Full_Path) {
 
download.file(url, destfile = basename(url), method="curl", extra="-k", mode="wb")

fl = list.files(full.names = T, pattern = '.png')

img = image_read(fl) # read from vector of paths

img2 = image_append(img, stack = TRUE) # places pics above one another

image_write(img2, format="pdf", file.path(dir,paste('IMG',today(),'.pdf'))) 

}

unlink(fl)

但是在这个循环之后全部打印在一个 PDF 中，我想为每个 ID 打印一个 pdf

Answer 1

我不确定下面的代码是否能回答问题。
输出文件名的名称中包含数字。

df <- data.frame(ID = c(1,1,2,2,3,3),
                 Full_Path = c("https://test1.png","https://test1.png",
                               "https://test1.png","https://test1.png",
                               "https://test1.png","https://test1.png"))

for(i in seq_len(nrow(df))) {
  url <- df$Full_Path[i]
  fl <- basename(url)
  download.file(url, destfile = fl, method="curl", extra="-k", mode="wb")
  img <- image_read(fl) # read from vector of paths
  img2 <- image_append(img, stack = TRUE) # places pics above one another
  
  # sprintf's format string outputs a string
  # with the formats replaced by
  #   %02d - an 2 digits integer padded with zeros
  #   %s   - a string, in this case the system date
  outfile <- sprintf('IMG_%02d_%s.pdf', i, today())
  outfile <- file.path(dir, outfile)
  image_write(img2, format = "pdf", outfile)
}

unlink(fl)