谢谢，可是还是不太懂呢，文件里比如说有一列是因子，有一列是数据；那么怎么只读入那一列是因子的一列呢？
然后怎么读入随机的某几行呢？

scan(file = "", what = double(), nmax = -1, n = -1, sep = "",
     quote = if(identical(sep, "\n")) "" else "'\"", dec = ".",
     skip = 0, nlines = 0, na.strings = "NA",
     flush = FALSE, fill = FALSE, strip.white = FALSE,
     quiet = FALSE, blank.lines.skip = TRUE, multi.line = TRUE,
     comment.char = "", allowEscapes = FALSE,
     fileEncoding = "", encoding = "unknown", text)

nmax integer: the maximum number of data values to be read, or if what is a list, the maximum number of records to be read. If omitted or not positive or an invalid value for an integer (and nlines is not set to a positive value), scan will read to the end of file.

n integer: the maximum number of data values to be read, defaulting to no limit. Invalid values will be ignored.

链接是http://stat.ethz.ch/R-manual/R-devel/library/base/html/scan.html

scan不是只能用来浏览数据类型文件么？

恩  懂了   谢谢    还是R手册上说的清楚