将长字符串转换为 data.frame
Convert long string to data.frame
这是一个菜鸟问题，但我对此很着迷。我有一个名为 bars.list 的字符向量，我从 FTP 服务器下载了它。矢量看起来像这样：
"\"\",\"times\",\"open\",\"high\",\"low\",\"close\",\"numEvents\",\"volume\"\r\n\"1\",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0\r\n\"2\",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0\r\n\"3\",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0\r\n\"4\",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0\r\n\"5\",2015-05-18 10:50:00,23.67,24.06,23.59,24.02,720,0\r\n\"6\",2015-05-18 11:50:00,24.02,24.04,23.32,23.33,720,0\r\n\"7\",2015-05-18 12:50:00,23.33,23.42,22.74,22.81,720,0\r\n\"8\",2015-05-18 13:50:00,22.79,22.92,22.49,22.69,720,0\r\n\"9\",2015-05-18 14:50:00,22.69,22.7,22.14,22.14,481,0\r\n\"10\",2015-05-19 06:50:00,21.09,21.49,20.82,21.47,421,0\r\n\"11\",2015-05-19 07:50:00,21.48,21.68,21.46,21.51,720,0\r\n\"12\",2015-05-19 08:50:00,21.51,21.93,21.45,21.92,720,0\r\n\"13\",2015-05-19 09:50:00,21.92,21.92,21.55,21.55,720,0\r\n\"
我需要将这个向量转换成可用的格式，但是
> read.table(bars.list, header = TRUE, sep = ",", quote = "", dec = ".")
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
cannot open file '"","times","open","high","low","close","numEvents","volume"
"1",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0
"2",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0
"3",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0
"4",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0
我不清楚为什么 R 告诉我无法打开某些连接，因为该对象已作为参数粘贴到函数中。输出 R Shows me with a warning sign 已经非常接近我需要的了...
这里有两个选项。第一个提供对当前代码的修复，第二个着眼于更简单、更高效的替代方案。
选项 1： read.table() 中的第一个参数是 file。您正在从矢量而不是文件中读取，因此您需要使用 text 参数和 text = bars.list.
此外，我们可以先去掉所有带 gsub() 的引号，然后再使用
read.csv() 而不是 read.table() 因为 header = TRUE 和 sep = "," 是默认值。
read.csv(text = gsub("\"", "", bars.list), row.names = 1)
# times open high low close numEvents volume
# 1 2015-05-18 06:50:00 23.98 23.98 23.50 23.77 421 0
# 2 2015-05-18 07:50:00 23.77 23.90 23.34 23.60 720 0
# 3 2015-05-18 08:50:00 23.60 23.60 23.32 23.42 720 0
# 4 2015-05-18 09:50:00 23.44 23.91 23.43 23.66 720 0
# 5 2015-05-18 10:50:00 23.67 24.06 23.59 24.02 720 0
# 6 2015-05-18 11:50:00 24.02 24.04 23.32 23.33 720 0
# 7 2015-05-18 12:50:00 23.33 23.42 22.74 22.81 720 0
# 8 2015-05-18 13:50:00 22.79 22.92 22.49 22.69 720 0
# 9 2015-05-18 14:50:00 22.69 22.70 22.14 22.14 481 0
# 10 2015-05-19 06:50:00 21.09 21.49 20.82 21.47 421 0
# 11 2015-05-19 07:50:00 21.48 21.68 21.46 21.51 720 0
# 12 2015-05-19 08:50:00 21.51 21.93 21.45 21.92 720 0
# 13 2015-05-19 09:50:00 21.92 21.92 21.55 21.55 720 0
对我来说，这比在 read.csv() 中使用 quote 参数效果更好。
选项 2：data.table 包中的 fread() 也很好用。它更快，代码更清晰。无需使用 gsub() 。我们可以直接把bars.list放进去，去掉第一列。
data.table::fread(bars.list, drop = 1)
现在，由于最后的 \" 引用，您将收到此方法的警告。您可以接受它，也可以通过删除最后一个引号来获得无警告的结果。
data.table::fread(sub("\"$", "", bars.list), drop = 1)
数据：
bars.list <- "\"\",\"times\",\"open\",\"high\",\"low\",\"close\",\"numEvents\",\"volume\"\r\n\"1\",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0\r\n\"2\",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0\r\n\"3\",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0\r\n\"4\",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0\r\n\"5\",2015-05-18 10:50:00,23.67,24.06,23.59,24.02,720,0\r\n\"6\",2015-05-18 11:50:00,24.02,24.04,23.32,23.33,720,0\r\n\"7\",2015-05-18 12:50:00,23.33,23.42,22.74,22.81,720,0\r\n\"8\",2015-05-18 13:50:00,22.79,22.92,22.49,22.69,720,0\r\n\"9\",2015-05-18 14:50:00,22.69,22.7,22.14,22.14,481,0\r\n\"10\",2015-05-19 06:50:00,21.09,21.49,20.82,21.47,421,0\r\n\"11\",2015-05-19 07:50:00,21.48,21.68,21.46,21.51,720,0\r\n\"12\",2015-05-19 08:50:00,21.51,21.93,21.45,21.92,720,0\r\n\"13\",2015-05-19 09:50:00,21.92,21.92,21.55,21.55,720,0\r\n\""
这是一个菜鸟问题，但我对此很着迷。我有一个名为 bars.list 的字符向量，我从 FTP 服务器下载了它。矢量看起来像这样：
"\"\",\"times\",\"open\",\"high\",\"low\",\"close\",\"numEvents\",\"volume\"\r\n\"1\",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0\r\n\"2\",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0\r\n\"3\",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0\r\n\"4\",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0\r\n\"5\",2015-05-18 10:50:00,23.67,24.06,23.59,24.02,720,0\r\n\"6\",2015-05-18 11:50:00,24.02,24.04,23.32,23.33,720,0\r\n\"7\",2015-05-18 12:50:00,23.33,23.42,22.74,22.81,720,0\r\n\"8\",2015-05-18 13:50:00,22.79,22.92,22.49,22.69,720,0\r\n\"9\",2015-05-18 14:50:00,22.69,22.7,22.14,22.14,481,0\r\n\"10\",2015-05-19 06:50:00,21.09,21.49,20.82,21.47,421,0\r\n\"11\",2015-05-19 07:50:00,21.48,21.68,21.46,21.51,720,0\r\n\"12\",2015-05-19 08:50:00,21.51,21.93,21.45,21.92,720,0\r\n\"13\",2015-05-19 09:50:00,21.92,21.92,21.55,21.55,720,0\r\n\"
我需要将这个向量转换成可用的格式，但是
> read.table(bars.list, header = TRUE, sep = ",", quote = "", dec = ".")
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
cannot open file '"","times","open","high","low","close","numEvents","volume"
"1",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0
"2",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0
"3",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0
"4",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0
我不清楚为什么 R 告诉我无法打开某些连接，因为该对象已作为参数粘贴到函数中。输出 R Shows me with a warning sign 已经非常接近我需要的了...
这里有两个选项。第一个提供对当前代码的修复，第二个着眼于更简单、更高效的替代方案。
选项 1： read.table() 中的第一个参数是 file。您正在从矢量而不是文件中读取，因此您需要使用 text 参数和 text = bars.list.
此外，我们可以先去掉所有带 gsub() 的引号，然后再使用
read.csv() 而不是 read.table() 因为 header = TRUE 和 sep = "," 是默认值。
read.csv(text = gsub("\"", "", bars.list), row.names = 1)
# times open high low close numEvents volume
# 1 2015-05-18 06:50:00 23.98 23.98 23.50 23.77 421 0
# 2 2015-05-18 07:50:00 23.77 23.90 23.34 23.60 720 0
# 3 2015-05-18 08:50:00 23.60 23.60 23.32 23.42 720 0
# 4 2015-05-18 09:50:00 23.44 23.91 23.43 23.66 720 0
# 5 2015-05-18 10:50:00 23.67 24.06 23.59 24.02 720 0
# 6 2015-05-18 11:50:00 24.02 24.04 23.32 23.33 720 0
# 7 2015-05-18 12:50:00 23.33 23.42 22.74 22.81 720 0
# 8 2015-05-18 13:50:00 22.79 22.92 22.49 22.69 720 0
# 9 2015-05-18 14:50:00 22.69 22.70 22.14 22.14 481 0
# 10 2015-05-19 06:50:00 21.09 21.49 20.82 21.47 421 0
# 11 2015-05-19 07:50:00 21.48 21.68 21.46 21.51 720 0
# 12 2015-05-19 08:50:00 21.51 21.93 21.45 21.92 720 0
# 13 2015-05-19 09:50:00 21.92 21.92 21.55 21.55 720 0
对我来说，这比在 read.csv() 中使用 quote 参数效果更好。
选项 2：data.table 包中的 fread() 也很好用。它更快，代码更清晰。无需使用 gsub() 。我们可以直接把bars.list放进去，去掉第一列。
data.table::fread(bars.list, drop = 1)
现在，由于最后的 \" 引用，您将收到此方法的警告。您可以接受它，也可以通过删除最后一个引号来获得无警告的结果。
data.table::fread(sub("\"$", "", bars.list), drop = 1)
数据：
bars.list <- "\"\",\"times\",\"open\",\"high\",\"low\",\"close\",\"numEvents\",\"volume\"\r\n\"1\",2015-05-18 06:50:00,23.98,23.98,23.5,23.77,421,0\r\n\"2\",2015-05-18 07:50:00,23.77,23.9,23.34,23.6,720,0\r\n\"3\",2015-05-18 08:50:00,23.6,23.6,23.32,23.42,720,0\r\n\"4\",2015-05-18 09:50:00,23.44,23.91,23.43,23.66,720,0\r\n\"5\",2015-05-18 10:50:00,23.67,24.06,23.59,24.02,720,0\r\n\"6\",2015-05-18 11:50:00,24.02,24.04,23.32,23.33,720,0\r\n\"7\",2015-05-18 12:50:00,23.33,23.42,22.74,22.81,720,0\r\n\"8\",2015-05-18 13:50:00,22.79,22.92,22.49,22.69,720,0\r\n\"9\",2015-05-18 14:50:00,22.69,22.7,22.14,22.14,481,0\r\n\"10\",2015-05-19 06:50:00,21.09,21.49,20.82,21.47,421,0\r\n\"11\",2015-05-19 07:50:00,21.48,21.68,21.46,21.51,720,0\r\n\"12\",2015-05-19 08:50:00,21.51,21.93,21.45,21.92,720,0\r\n\"13\",2015-05-19 09:50:00,21.92,21.92,21.55,21.55,720,0\r\n\""