二进制文件是一个文件，其中包含仅以位和字节形式存储的信息(0和1)，它们是不可读的，因为其中的字节转换为包含许多其他不可打印字符的字符和符号，随便我们尝试使用任何文本编辑器读取二进制文件将显示为类似Ø和ð这样的字符。
但是二进制文件必须由特定程序读取才能使用。例如，Microsoft Word程序的二进制文件只能通过Word程序读取到人类可读的形式。这表明，除了人类可读的文本之外，还有更多的信息，如格式化的字符和页码等，它们也与字母数字字符一起存储。最后，二进制文件是一个连续的字节序列。 我们在文本文件中看到的换行符是将第一行连接到下一个的字符。
有时，由其他程序生成的数据需要由R作为二进制文件处理，另外R需要创建可以与其他程序共享的二进制文件，在R中有两个函数用来创建和读取二进制文件，它们分别是：WriteBin()和readBin()函数，来看下语法：
writeBin(object, con) readBin(con, what, n )
参数描述如下：
con - 是要读取或写入二进制文件的连接对象。 object - 是要写入的二进制文件。 what - 是像字符，整数等的模式，代表要读取的字节。 n - 是从二进制文件读取的字节数。我们接下来使用R内置数据“mtcars”创建一个csv文件并将其转换为二进制文件并将其存储为操作系统文件，如下：
#my first R program
# Read the "mtcars" data frame as a csv file and store only the columns "cyl", "am" and "gear".
write.table(mtcars, file = "mtcars.csv",row.names = FALSE, na = "",
col.names = TRUE, sep = ",")
# Store 5 records from the csv file as a new data frame.
new.mtcars <- read.table("mtcars.csv",sep = ",",header = TRUE,nrows = 5)
# Create a connection object to write the binary file using mode "wb".
write.filename = file("D:/r_file/binmtcars.dat", "wb")
# Write the column names of the data frame to the connection object.
writeBin(colnames(new.mtcars), write.filename)
# Write the records in each of the column to the file.
writeBin(c(new.mtcars$cyl,new.mtcars$am,new.mtcars$gear), write.filename)
# Close the file for writing so that it can be read by other program.
close(write.filename)
运行上面的文件就会产生一个csv文件和一个dat二进制文件。这个dat文件将所有数据作为连续字节存储， 因此，我们将通过选择列名称和列值的适当值来读取它，如下：
#my first R program
# Create a connection object to read the file in binary mode using "rb".
read.filename <- file("D:/r_file/binmtcars.dat", "rb")
# First read the column names. n = 3 as we have 3 columns.
column.names <- readBin(read.filename, character(), n = 3)
# Next read the column values. n = 18 as we have 3 column names and 15 values.
read.filename <- file("D:/r_file/binmtcars.dat", "rb")
bindata <- readBin(read.filename, integer(), n = 18)
# Print the data.
print(bindata)
# Read the values from 4th byte to 8th byte which represents "cyl".
cyldata = bindata[4:8]
print(cyldata)
# Read the values form 9th byte to 13th byte which represents "am".
amdata = bindata[9:13]
print(amdata)
# Read the values form 9th byte to 13th byte which represents "gear".
geardata = bindata[14:18]
print(geardata)
# Combine all the read values to a dat frame.
finaldata = cbind(cyldata, amdata, geardata)
colnames(finaldata) = column.names
print(finaldata)
上述代码演示了几种输出的方式，大家有兴趣的可以自己扩展下。
