R:進階-Tidyverse和條件循環(huán)

Tidyverse

《R數(shù)據(jù)科學(xué)》(大神全套體系)

  • ggplot2:數(shù)據(jù)可視化
  • dplyr:數(shù)據(jù)轉(zhuǎn)換和處理數(shù)據(jù)關(guān)系
  • readr:數(shù)據(jù)導(dǎo)入
  • stringr:處理字符串

一、tidyr

數(shù)據(jù)清理,轉(zhuǎn)化為標準表格,tidydata每個變量(variable)占一列,每個觀測(observation)占一行

1. 數(shù)據(jù)清理

test <- data.frame(geneid = paste0("gene",1:4),
                 sample1 = c(1,4,7,10),
                 sample2 = c(2,5,0.8,11),
                 sample3 = c(0.3,6,9,12))
test
(1)扁變長
test_gather <- gather(data = test,
                    key = sample_nm,
                    value = exp,
                    - geneid)
head(test_gather)
(2)長變扁
test_re <- spread(data = test_gather,
                key = sample_nm,
                value = exp)
head(test_re)

2. 分割和合并

test <- data.frame(x = c( "a,b", "a,d", "b,c"));test
(1)分割
test_seprate <- separate(test,x, c("X", "Y"),sep = ",");test_seprate
(2)合并
test_re <- unite(test_seprate,"x",X,Y,sep = ",")

3. 處理NA

X<-data.frame(X1 = LETTERS[1:5],X2 = 1:5)
X[2,2] <- NA
X[4,1] <- NA
(1)去掉含有NA的行,可以選擇只根據(jù)某一列來去除
drop_na(X)
drop_na(X,X1)
drop_na(X,X2)
(2)替換NA
replace_na(X$X2,0)
(3)用上一行的值填充NA
fill(X,X2)

完整操作:https://www.rstudio.com/resources/cheatsheets/

二、dplyr

test <- iris[c(1:2,51:52,101:102),]
rownames(test) =NULL

1. 五個基礎(chǔ)函數(shù)

(1)mutate():新增列
mutate(test, new = Sepal.Length * Sepal.Width)
test$new = test$Sepal.Length * test$Sepal.Width #base包方式
(2)select():按列篩選
  • 按列號篩選
select(test,1)
select(test,c(1,5))
  • 按列名篩選
select(test,Sepal.Length)
select(test, Petal.Length, Petal.Width)
vars <- c("Petal.Length", "Petal.Width")
select(test, one_of(vars))
  • 一組來自tidyselect的有用函數(shù)
select(test, starts_with("Petal"))
select(test, ends_with("Width"))
select(test, contains("etal"))
select(test, matches(".t."))
select(test, everything())
select(test, last_col())
select(test, last_col(offset = 1))
  • 利用everything() 列名可以重排序
select(test,Species,everything())
(3)filter():篩選行
filter(test, Species == "setosa")
filter(test, Species == "setosa"&Sepal.Length > 5 )
filter(test, Species %in% c("setosa","versicolor"))
(4)arrange():按某一列對整個表格進行排序
arrange(test, Sepal.Length) #默認從小到大排序
arrange(test, desc(Sepal.Length)) #desc即從大到小
arrange(test, desc(Sepal.Width),Sepal.Length) #但兩行相同時,亞條件排序
(5)summarise():匯總

對數(shù)據(jù)進行匯總操作,結(jié)合group_by使用實用性強

summarise(test, mean(Sepal.Length), sd(Sepal.Length)) #計算Sepal.Length的平均值和標準差
# 先按照Species分組,計算每組Sepal.Length的平均值和標準差
group_by(test, Species)
tmp = summarise(group_by(test, Species),mean(Sepal.Length), sd(Sepal.Length))

2. 兩個實用技能

(1)管道操作 %>% (cmd/ctr + shift + M)
library(dplyr)
x1 = filter(iris,Sepal.Width>3)
x2 = select(x1,c("Sepal.Length","Sepal.Width" ))
x3 = arrange(x2,Sepal.Length)
colnames(iris)
iris %>% 
  filter(Sepal.Width>3) %>% 
  select(c("Sepal.Length","Sepal.Width" ))%>%
  arrange(Sepal.Length)
#上一行結(jié)果做下一行的主對象
(2)count:統(tǒng)計某列的unique值
count(test,Species) #數(shù)據(jù)框
table(test$Species) #base包,向量

3. 處理關(guān)系數(shù)據(jù):將2個表進行連接,注意:不要引入factor

options(stringsAsFactors = F)
test1 <- data.frame(name = c('jimmy','nicker','doodle'), 
                    blood_type = c("A","B","O"))
test1
test2 <- data.frame(name = c('doodle','jimmy','nicker','tony'),
                    group = c("group1","group1","group2","group2"),
                    vision = c(4.2,4.3,4.9,4.5))
test2 
test3 <- data.frame(NAME = c('doodle','jimmy','lucy','nicker'),
                    weight = c(140,145,110,138))
merge(test1,test2,by="name")
merge(test1,test3,by.x = "name",by.y = "NAME")
(1)內(nèi)連inner_join:取交集,相同行,合并列
inner_join(test1, test2, by = "name")
inner_join(test1,test3,by = c("name"="NAME"))
(2)左連left_join:取主表行,合并列,缺失值NA
left_join(test1, test2, by = 'name') #前為主表
left_join(test2, test1, by = 'name')
(3)全連full_join:全兩表所有行,合并列
full_join(test1, test2, by = 'name')
(4)半連接:返回能夠與y表匹配的x表所有記錄,取x與y表相同行,x所有列
semi_join(x = test1, y = test2, by = 'name')
(5)反連接:返回?zé)o法與y表匹配的x表的所記錄 取x與y表差異行,x所有列
anti_join(x = test2, y = test1, by = 'name')
(6)數(shù)據(jù)的簡單合并
  • 相當于base包里的cbind()函數(shù)和rbind()函數(shù)
  • bind_rows()函數(shù)需要兩個表格列數(shù)相同,而bind_cols()函數(shù)則需要兩個數(shù)據(jù)框有相同的行數(shù)
test1 <- data.frame(x = c(1,2,3,4), y = c(10,20,30,40))
test1
test2 <- data.frame(x = c(5,6), y = c(50,60))
test2
test3 <- data.frame(z = c(100,200,300,400))
test3
bind_rows(test1, test2)
bind_cols(test1, test3)

三、stringr

image.png
x <- "The birch canoe slid on the smooth planks."
x

1. 檢測字符串長度

length(x) #向量長度
str_length(x) #字符長度

2. 字符串拆分與組合

str_split(x," ") #列表
x2 = str_split(x," ")[[1]] #取列表
y = c("jimmy 150","nicker 140","tony 152")
str_split(y," ")
str_split(y," ",simplify = T) #simplify后得到矩陣
str_c(x2,collapse = " ") #x2的所有元素按空格“ ”連接在一起
str_c(x2,1234,sep = "+") #兩個參數(shù)

3. 提取字符串的一部分

str_sub(x,5,9)

4. 大小寫轉(zhuǎn)換

str_to_upper(x2)
str_to_lower(x2)
str_to_title(x2)

5. 字符串定位

str_locate(x2,"th")
str_locate(x2,"h")

6. 字符檢測

str_detect(x2,"h") #生成與X2等長的邏輯向量,可以取子集
str_starts(x2,"T")
str_ends(x2,"e")

與sum和mean連用,可以統(tǒng)計匹配的個數(shù)和比例

sum(str_detect(x2,"h")) #Ture的個數(shù)
mean(str_detect(x2,"h")) #Ture占全部的比例

7. 提取匹配到的字符串

str_extract(x2,"th|Th") #|或者,默認提取第一次出
str_extract_all(x2,"o") #列表
str_extract_all(x2,"o",simplify = T) #矩陣,“”空字符串

8. 字符刪除

str_remove(x," ") #只刪掉第一個
str_remove_all(x," ")  #刪除所有
str_remove_all(x2,"th")

9. 字符串替換

str_replace(x2,"o","A") #只替換第一個
str_replace_all(x2,"o","A")

結(jié)合正則表達式更加強大

條件語句和循環(huán)語句

一、條件語句

1.if(){ }

(1)只有if沒有else,那么條件是FALSE時就什么都不做,只有一個邏輯值
i = -1
if (i<0) print('up')
if (i>0) print('up')
#理解下面代碼
if(!require(tidyr)) install.packages('tidyr')
(2)有else:只有一個邏輯值
i =1
if (i>0){
  cat('+') #看看里面是什么內(nèi)容 
} else {
  print("-") #向量
}
(3)ifelse:自帶循環(huán)屬性,可以有多個邏輯值,重點!
ifelse(i>0,"+","-") 
x=rnorm(3)
ifelse(x>0,"+","-")
(4)多個條件
i = 0
if (i>0){
  print('+')
} else if (i==0) {
  print('0')
} else if (i< 0){
  print('-')
}
ifelse(i>0,"+",ifelse((i<0),"-","0"))

2. switch()

cd = 3
foo <- switch(EXPR = cd, 
              #EXPR = "aa", 
              aa=c(3.4,1),
              bb=matrix(1:4,2,2),
              cc=matrix(c(T,T,F,T,F,F),3,2),
              dd="string here",
              ee=matrix(c("red","green","blue","yellow")))
foo

二、循環(huán)語句

1.f or循環(huán)

#**順便看一下next和break**
x <- c(5,6,0,3)
s=0
for (i in x){
  s=s+i
  #if(i == 0) next
  #if (i == 0) break
  print(c(i,s))
}
#x下標循環(huán)
x <- c(5,6,0,3)
s = 0
for (i in 1:length(x)){
  s=s+x[[i]]
  print(c(x[[i]],s))
}

如何將結(jié)果存下來?

s = 0
result = list()  #先聲明是列表,然后往列表里一個一個加元素
for(i in 1:length(x)){
  s=s+x[[i]]
  result[[i]] = c(x[[i]],s)
}
do.call(cbind,result)

2. while 循環(huán)

i = 0
while (i < 5){
  print(c(i,i^2))
  i = i+1
}

3. repeat 語句

#注意:必須有break
i=0L
s=0L
repeat{
 i = i + 1
 s = s + i
 print(c(i,s))
 if(i==50) break
}

4. apply函數(shù)

  • apply(x,MARGIN,FUN)
  • x是數(shù)據(jù)框/矩陣名
  • MARGIN為1表示取行,2表示取列
  • FUN是函數(shù)
  • 對x的每一行/列進行FUN這個函數(shù)
  • sapply(list,fun) #對列表進行循環(huán)

插播

長腳本管理方式

1. 分成多個腳本,每個腳本最后將變量保存到Rdata,下一個腳本開頭清空再加載
image.png

image.png
2. 折疊長代碼{}

利用if(F)和if(T),只有if(T)會運行


image.png

自己寫嵌套代碼從外往里寫,讀別人的嵌套代碼從里往外讀

實戰(zhàn)重點函數(shù)

  • sort和match
  • names
  • ifelse和str_detect
  • identical
  • arrange
  • merge和inner_join
  • unique和duplicated

R語言遍歷、創(chuàng)建、刪除文件夾

dir
file.create() file.exists(...)
file.remove()
file.rename(from,to)
file.append(file1, file2)
file.copy(from, to, overwrite = recursive, recursive = FALSE, copy.mode = TRUE, copy.date = FALSE)
file.symlink(from,to)
file.link(from, to)
dir.create('doudou')
unlink("doudou",recursive =T)
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