title: "R语言实战2：数据结构"
author: "wintryheart"
date: "2019年5月17日"
output: html_document

knitr::opts_chunk$set(echo = TRUE)

第2章 创建数据集

2.1 数据集的概念

各行业对数据集的行和列的不同叫法：

2.2 数据结构

实例

# 向量
a <- c(1, 2, 3)
b <- c("best", "better", "good")
c <- c(TRUE, FALSE, TRUE)
a
b
c

# 矩阵

x <- matrix(1:20, nrow=5, ncol=4)
y1 <- matrix(1:20, nrow=5, ncol=4, byrow = TRUE)
y2 <- matrix(1:20, nrow=5, ncol=4, byrow = FALSE)
x
y1
y2
rnames <- c("R1", "R2")
cnames <- c("C1", "C2")
y3 <- matrix(1:20, nrow=2, ncol=2, dimnames = list(rnames, cnames))
y3
# 数组
dim1 <- c("A1", "A2")
dim2 <- c("B1", "B2", "B3")
dim3 <- c("C1", "C2", "C3", "C4")
array1 <- array(1:24, c(2,3,4))
array1
array2 <- array(1:24, c(2,3,4), dimnames= list(dim1, dim2, dim3))
array2
#数据框
patientID <- c(1,2,3,4)
age <- c(25, 34,28, 52)
diabetes <- c("Type1", "Type2", "Type1", "Type1")
status <- c("Poor", "Improved", "Excellent", "Poor")
patientdata <- data.frame(patientID, age, diabetes, status)
patientdata

#选取行
patientdata[1:2]
#选取列
patientdata[c("diabetes", "status")]
#交叉表
table(patientdata$diabetes, patientdata$status)

# attach(), detach()和with()
attach(patientdata)
summary(age)
detach(patientdata)

with(patientdata, {
  summary(age)
})

#with()创建的对象只在括号内有效。
#如果要创建with()结构以外存在的对象，使用特殊赋值符 <<- 代替标准赋值符 <-
with(patientdata, {
   inkeep <- summary(age)
   outkeep <<- summary(age)
})

outkeep

#因子
attach(patientdata)
diabetes
diabetes <- factor(diabetes)
diabetes

status
status <- factor(status, ordered = TRUE)
status
#自定义排序
status <- factor(status, ordered = TRUE, levels = c("Poor", "Improved", "Excellent"))
status
#显示对象的结构
str(patientdata)
summary(patientdata)

#列表

g <- "My list"
h <- c(25, 26, 18 ,39)
j <- matrix(1:10, nrow=5)
k <- c("one", "two", "three")
mylist <- list(title=g, age=h, j, k)
mylist
#显示列表中的某个对象
mylist[[2]]
mylist[["age"]]

2.3 数据输入

2.4数据集的标注

• 变量标签：不支持
• 值标签： factor()函数中的labels参数

patientdata$gender <- c(1,2,1,1)
patientdata$gender <- factor(patientdata$gender, levels=c(1,2), labels=c("male", "female"))
patientdata["gender"]