R语言学习之数据的清理和转化
处理字符串
grep grepl 和regexpr函数都能找到与模式相匹配的字符串 sub 和 gsub函数能替换匹配的字符串
加载strngr包，fixed里面为要匹配的字符串 返回匹配的字符串序列
> library(stringr)
> multiple <- str_detect(english_monarchs$domain,fixed(","))
> english_monarchs[multiple,c("name","domain")]
name domain
17 Offa East Anglia, Mercia
18 Offa East Anglia, Kent, Mercia
19 Offa and Ecgfrith East Anglia, Kent, Mercia
20 Ecgfrith East Anglia, Kent, Mercia
22 C<U+009C>nwulf East Anglia, Kent, Mercia
23 C<U+009C>nwulf and Cynehelm East Anglia, Kent, Mercia
24 C<U+009C>nwulf East Anglia, Kent, Mercia
25 Ceolwulf East Anglia, Kent, Mercia
26 Beornwulf East Anglia, Mercia
82 Ecgbehrt and <U+00C6>thelwulf Kent, Wessex
83 Ecgbehrt and <U+00C6>thelwulf Kent, Mercia, Wessex
84 Ecgbehrt and <U+00C6>thelwulf Kent, Wessex
85 <U+00C6>thelwulf and <U+00C6>eelstan I Kent, Wessex
86 <U+00C6>thelwulf Kent, Wessex
87 <U+00C6>thelwulf and <U+00C6>eelberht III Kent, Wessex
88 <U+00C6>eelberht III Kent, Wessex
89 <U+00C6>thelred I Kent, Wessex
95 Oswiu Mercia, Northumbria
使用正则表达式来匹配多个要匹配的字符串，这是来匹配逗号和and
> ruler <- str_detect(english_monarchs$name,",|and") > english_monarchs[ruler & !is.na(ruler)]把name一列拆分掉，则可以使用str_splist函数
> indival <- str_split(english_monarchs$name,",|and") > head(indival[sapply(indival,length)>1]) [[1]] [1] "Sigeberht " " Ecgric" [[2]] [1] "Hun" " Beonna " " Alberht" [[3]] [1] "Offa " " Ecgfrith" [[4]] [1] "C\u009cnwulf " " Cynehelm" [[5]] [1] "Sighere " " Sebbi" [[6]] [1] "Sigeheard " " Swaefred"
st_count是用来统计有多少个字符串
> str_count(english_monarchs$name,th)
str_replace函数来代替字符串中的某一个
ignore.case来忽略某一个字符或字符串