R语言字符串处理①R语言字符串合并与拆分

library(DiagrammeR)
grViz("
      digraph boxes_and_circles {
      graph [rankdir = LR]
      字符处理需求->{拼接 拆分（根据pattern） 替换 提取}
      拼接->{多拼为一 对应拼接}
      替换->{根据位置 根据pattern（正则表达式）}
      提取->{根据位置 根据pattern（正则表达式）}}")

a <- c("2016-2-7","2016-3-8","2016-4-9","2017-5-10")
b <- c("ahdbca","bhdafb")

nchar(a) # 计算字符串中字符个数

paste(a,b,sep="--")  # 对应拼接
paste(a,collapse ="  ") # 拼接成一个字符串
paste(a,b,sep="--",collapse ="  ")  # 两步合成一步

strsplit(a,split="-") # 拆分
strsplit(a,split="-\\d-",fixed=F) # 使用正则表达式拆分
# 使用|或来按照两种形式拆分
q <- c("a-b.c-d")
strsplit(q,"\\.|-") # "a" "b" "c" "d"

# 改变字符串
# 大小写转换
(c <- toupper(b))
tolower(c)
casefold(c)
casefold(b,upper=T)

chartr("ab","mn",b) # 对应替换,不支持正则表达式
gsub(pattern="-\\d-",replacement="B",a) # 搜索匹配的内容替换全部
sub(pattern="-",replacement="B",a) # 搜索匹配的内容,只替换第一个

library(DiagrammeR)
grViz("
      digraph boxes_and_circles {
      graph [rankdir = LR]
      字符处理需求->{拼接 拆分（根据pattern） 替换 提取}
      拼接->{多拼为一 对应拼接}
      替换->{根据位置 根据pattern（正则表达式）}
      提取->{根据位置 根据pattern（正则表达式）}}")


library(dplyr)
library(stringr)
library(tidyr)
myyear<-sprintf("20%02d",sample(0:17,10))
mymonth<-sprintf("%02d",sample(0:12,10))
myday<-sprintf("%02d",sample(0:31,10))
myyear;mymonth;myday

full<-paste(myyear,mymonth,myday,sep = "-");full  



myyear1=mymonth1=myday1=NULL
for( i in 1:length(full)){
  myyear1[i]<-strsplit(full[i],"-")[[1]][1]
  mymonth1[i]<-strsplit(full[i],"-")[[1]][2]
  myday1[i]<-strsplit(full[i],"-")[[1]][3]
}
myyear1;mymonth1;myday1





myyear1=mymonth1=myday1=NULL
for( i in 1:length(full)){
  myyear1[i]<-str_split(full[i],"-")[[1]][1]
  mymonth1[i]<-str_split(full[i],"-")[[1]][2]
  myday1[i]<-str_split(full[i],"-")[[1]][3]
}






mydata1<-unite(mydata,col="datetime",
               c("myyear","mymonth","myday"),
               sep="-",remove=FALSE);mydata1



mydata2<-unite(mydata1,col="datetime1",
               c("myyear","mymonth","myday"),
               sep="-",remove=FALSE);mydata2