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  • R语言笔记

    近期做的几个项目都是用R语言来完毕的。正如老师所说。学起来非常快。忘起来也非常快。整理一下放在这里,方便以后查阅。



    安装所需的包:
    install.packages("xxxx")

    载入包:
    library("xxxx")

    显示/改变工作文件夹
    getwd()/setwd("d:/temp")

    文件操作:
    1.读取csv文件
    var=read.csv("demo.csv",header=FALSE)——header表示是否有表头。默觉得TRUE

    2.读取数据文件
    data=read.table("demo.data")

    3.读取文本文件
    var=readLines("demo.txt",encoding="UTF-8")

    4.输出csv文件
    write.csv(var,"var.csv")

    5.输出普通文本文件
    write(var,"var.txt")

    6.把整个执行空间保存到文件
    save.image("demo.RData")

    7.读取文件到执行空间
    load("demo.RData")

    清除执行空间所有变量:
    rm(list=ls())

    字符串操作:
    1.获取字符串长度
    nchar("asdf")——与length是不同的

    2.连接字符串
    paste("abc","def")——默认用空格间隔。若取消间隔。可用參数sep=""

    3.切割字符串
    str1=strsplit("abc def"," ")——切割结果是list类型,如需转成向量使用str1=unlist(strsplit("abc def"," "))

    4.字符串截取
    substr("hello",2,3)——參数表示起止位置

    5.字符串替代
    gsub("a","c","asdfasdf")——把asdfasdf替换成csdfcsdf

    6.字符串匹配
    grep("oo",c("hello","world","good"))——搜索给定字符串中的特定表达式 。返回其位置索引

    集合(向量)操作:
    1.求交集
    intersect(c("a","b","c"),c("a","c","d"))

    2.求并集
    union(c("a","b","c"),c("a","c","d"))

    3.求差集
    setdiff(c("a","b","c"),c("a","c","d"))

    4.向量去重
    unique(c("a","b","a","c"))

    5.向量排序
    sort(c("a","b","a","c"))/rev(sort(c("a","b","a","c")))

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  • 原文地址:https://www.cnblogs.com/clnchanpin/p/6815679.html
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