R version 3.3.2 使用read.table读取ascii数据时报错，不知道我哪里处理不当，求指点
附件是我练习用的xls文件

我操作的步骤是：
删除xls文件第二行空的单元格
删除xls文件第一行和第三行那些英文之间的空格
将xls另存为文本文件（制表符分隔）
在R中设置工作目录后，用read.table读取txt文件
报错如下
> setwd("D:/R/RExer")
> Isit<-read.table(file="ISIT3.txt",header=TRUE,dec=".")
Error in make.names(col.names, unique = TRUE) :
invalid multibyte string at '<ff><fe><54>'
In addition: Warning messages:
1: In read.table(file = "ISIT3.txt", header = TRUE, dec = ".") :
line 1 appears to contain embedded nulls
2: In read.table(file = "ISIT3.txt", header = TRUE, dec = ".") :
line 2 appears to contain embedded nulls
3: In read.table(file = "ISIT3.txt", header = TRUE, dec = ".") :
line 3 appears to contain embedded nulls
4: In read.table(file = "ISIT3.txt", header = TRUE, dec = ".") :
line 4 appears to contain embedded nulls
5: In read.table(file = "ISIT3.txt", header = TRUE, dec = ".") :
line 5 appears to contain embedded nulls


这是<A Beginner's Guide to R>第二章的第6道习题，官网上给的操作指导如下：
#Section 2.4. Exercise 6#There are empty cells and variable names with spaces#Remove the spaces in variable names and empty cells#should be replaced by an NA#This code is computer specific.#On a Mac use:setwd("/Users/Highstat/applicat/HighlandStatistics/Courses/FilesBeginnersGuide2R/BeginnersGuideToR/Data")#On a Windows OS computer use:setwd("Z:/Users/Highstat/applicat/HighlandStatistics/Courses/FilesBeginnersGuide2R/BeginnersGuideToR/Data")#You need to replace the entire path by the directory in which you #saved the data. BioLum <- read.table(file = "ISIT.txt", header = TRUE, dec = ".")BioLum2 <- scan(file = "ISIT.txt", skip = 1, dec = ".")#read.table is more user friendly#can is useful for large data sets.names(BioLum)str(BioLum)
我不知道我是不是漏了哪一步？求教求教~