R语言day3：数据框是什么玩意儿？
原创R语言day3：数据框是什么玩意儿？
原创
不会写代码的医学生
修改于 2024-03-11 11:32:45
修改于 2024-03-11 11:32:45
title: "day3note"
output: html_document
date: "2024-03-08"
#重点：数据框
1.数据框来源
（1）用代码新建
（2）由已有数据转换或处理得到
（3）读取表格文件
（4）R语言内置数据 iris
2.新建和读取数据框
新建数据框
#赋值 #列名
df1 <- data.frame(gene = paste0("gene",1:4),
change = rep(c("up","down"),each = 2),
score = c(5,3,-2,-4))
df1## gene change score
## 1 gene1 up 5
## 2 gene2 up 3
## 3 gene3 down -2
## 4 gene4 down -4从文件读取
df2 <- read.csv("gene.csv")df2
3.数据框属性
dim(df1) #行和列## [1] 4 3nrow(df1) #行## [1] 4ncol(df1) #列## [1] 3#
rownames(df1) #行名## [1] "1" "2" "3" "4"colnames(df1) #列名## [1] "gene" "change" "score"
4.数据框取子集
$ #取列
df1$score #删掉score，按tab键试试
mean(df1$score)4.1按坐标
df1[2,2]## [1] "up"df1[2,] #取第2行所有列## gene change score
## 2 gene2 up 3df1[,2]## [1] "up" "up" "down" "down"df1[c(1,3),1:2] #取第一行和第三行，第一列到第二列## gene change
## 1 gene1 up
## 3 gene3 down
4.2按名字
df1[,"gene"]## [1] "gene1" "gene2" "gene3" "gene4"df1[,c('gene','change')]## gene change
## 1 gene1 up
## 2 gene2 up
## 3 gene3 down
## 4 gene4 down5.数据框修改
#改一个格
df1[3,3] <- 5
df1## gene change score
## 1 gene1 up 5
## 2 gene2 up 3
## 3 gene3 down 5
## 4 gene4 down -4#改一整列
df1$score <- c(12,23,50,2)
df1## gene change score
## 1 gene1 up 12
## 2 gene2 up 23
## 3 gene3 down 50
## 4 gene4 down 2#？
df1$p.value <- c(0.01,0.02,0.07,0.05)
df1## gene change score p.value
## 1 gene1 up 12 0.01
## 2 gene2 up 23 0.02
## 3 gene3 down 50 0.07
## 4 gene4 down 2 0.05小提示：哪个是修改，哪个是增加一列？
5.1改行名和列名
rownames(df1) <- c("r1","r2","r3","r4")
#只修改某一行/列的名
colnames(df1)[2] <- "CHANGE" #第二列列名改为CHANGE6.两个数据框的连接
test1 <- data.frame(name = c('jimmy','nicker','Damon','Sophie'),
blood_type = c("A","B","O","AB"))
test1## name blood_type
## 1 jimmy A
## 2 nicker B
## 3 Damon O
## 4 Sophie ABtest2 <- data.frame(name = c('Damon','jimmy','nicker','tony'),
group = c("group1","group1","group2","group2"),
vision = c(4.2,4.3,4.9,4.5))
test2## name group vision
## 1 Damon group1 4.2
## 2 jimmy group1 4.3
## 3 nicker group2 4.9
## 4 tony group2 4.5test3 <- data.frame(NAME = c('Damon','jimmy','nicker','tony'),
weight = c(140,145,110,138))
test3## NAME weight
## 1 Damon 140
## 2 jimmy 145
## 3 nicker 110
## 4 tony 138merge(test1,test2,by="name")## name blood_type group vision
## 1 Damon O group1 4.2
## 2 jimmy A group1 4.3
## 3 nicker B group2 4.9merge(test1,test3,by.x = "name",by.y = "NAME")## name blood_type weight
## 1 Damon O 140
## 2 jimmy A 145
## 3 nicker B 110
7.矩阵和列表
m <- matrix(1:9, nrow = 3) #将一个矩阵3行9个元素赋值给m
colnames(m) <- c("a","b","c") #加列名
m## a b c
## [1,] 1 4 7
## [2,] 2 5 8
## [3,] 3 6 9m[2,]## a b c
## 2 5 8m[,1]## [1] 1 2 3m[2,3]## c
## 8m[2:3,1:2] #取m2到3行，1到2列## a b
## [1,] 2 5
## [2,] 3 6
并没有，因为没有赋值，r语言任何修改都要赋值，没赋值就等于没发生过
m## a b c
## [1,] 1 4 7
## [2,] 2 5 8
## [3,] 3 6 9t(m) #转置m## [,1] [,2] [,3]
## a 1 2 3
## b 4 5 6
## c 7 8 9
as.data.frame(m)## a b c
## 1 1 4 7
## 2 2 5 8
## 3 3 6 97.1列表
x <- list(m1 = matrix(1:9, nrow = 3),
m2 = matrix(2:9, nrow = 2))
x## $m1
## [,1] [,2] [,3]
## [1,] 1 4 7
## [2,] 2 5 8
## [3,] 3 6 9
##
## $m2
## [,1] [,2] [,3] [,4]
## [1,] 2 4 6 8
## [2,] 3 5 7 9x[[1]] ## [,1] [,2] [,3]
## [1,] 1 4 7
## [2,] 2 5 8
## [3,] 3 6 9x[[""]]x$m1## [,1] [,2] [,3]
## [1,] 1 4 7
## [2,] 2 5 8
## [3,] 3 6 97.2补充：元素的名字-names()
scores = c(100,59,73,95,45)
names(scores) = c("jimmy","nicker","Damon","Sophie","tony")
scores## jimmy nicker Damon Sophie tony
## 100 59 73 95 45scores["jimmy"]## jimmy
## 100scores[c("jimmy","nicker")]## jimmy nicker
## 100 59names(scores)[scores>60]## [1] "jimmy" "Damon" "Sophie"8.后置的难点
8.1按条件（逻辑值）
df1 <- data.frame(gene = paste0("gene",1:4),
change = rep(c("up","down"),each = 2),
score = c(5,3,-2,-4))
k = df1$score>0;k #将score>0的列取出来## [1] TRUE TRUE FALSE FALSEdf1[k,] #将score>0的行取出来## gene change score
## 1 gene1 up 5
## 2 gene2 up 3
8.2筛选score > 0的基因
df1[k,1] #将score这列的score>0的行取出来## [1] "gene1" "gene2"df1$gene[k]#gene这列的score>0的行取出来## [1] "gene1" "gene2"df1$gene[df1$score>0]## [1] "gene1" "gene2"9.删除
rm(x) #删除一个
rm(df1,df2) #删除多个
rm(list = ls()) #删除全部
原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。
如有侵权，请联系 cloudcommunity@tencent.com 删除。
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