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单选题 txt<-c("the","most","software","are","to","take","freedom"),sub("[te]","h", txt)=( )
学科：数据分析与R语言
时间：2024-12-01 14:36:00
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题目1单选题
下列关于函数grep()和grepl()说法错误的是( )A. grep()函数可以查询字符串,默认的返回结果为匹配项的下标B. grepl()函数也用于字符串的查询和替换,它返回一个逻辑向量C. grep()函数可以查询字符串,若参数value=TRUE时,返回结果为匹配项的下标D. grep()函数可以查询字符串,若参数value=TRUE时,返回结果为匹配项的值
题目2单选题
x <- "晴空一鹤排云上,便引诗情到碧霄",substring(x,5)的运行结果为( )A. Error in substring(x, 5) : 缺少参数"stop",也没有缺省值B. "排云上,便引诗情到碧霄"C. "排"D. "晴空一鹤排云上,便引诗情到碧霄"
题目3单选题
x <- "晴空一鹤排云上,便引诗情到碧霄",n <- nchar(x),substr(x,1:n,1:n)的运行结果为( )A. "晴" "霄"B. "晴空一鹤排云上,便引诗情到碧霄"C. "霄"D. "晴"
题目4单选题
txt<-c("the","most","software","are","to","take","freedom"),sub("[te]","h", txt)=( )A. "hhh" "mosh" "sofhwarh" "arh" "ho" "hakh" "frhhdom"B. "hhe" "mosh" "sofhwarh" "arh" "ho" "hakh" "frhhdom"C. "hhh" "mosh" "sofhware" "arh" "ho" "hakh" "frhhdom"D. "hhe" "mosh" "sofhware" "arh" "ho" "hake" "frhedom"
题目5填空题
匹配除了5以外的任何字符的正则表达式为____题目6填空题
匹配1或2的正则表达式为____题目7填空题
使用正则表达式的规则进行匹配的函数是____题目8填空题
匹配以e结尾的正则表达式为____题目9填空题
若x <- "apples x4",则nchar(x)=____题目10填空题
若x <- "apples x4",则length(x)=____下载 题海APP
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