R04

x = "The birch canoe slid on the smooth planks."
str_length(x)
[1] "The birch canoe slid on the smooth planks."
length(x)
[1] 1

str_split(x," ")
[[1]]
"The"     "birch"   "canoe"   "slid"    "on"      "the"    "smooth"    "planks."

x2 = str_split(x," ")[[1]];x2
[1]"The"     "birch"   "canoe"   "slid"    "on"      "the"    "smooth"  "planks."

str_sub(x,5,9)
[1]"birch"

str_sub(x,6,9)
[1]"irch"

str_detect(x2,"h")
[1]  TRUE  TRUE FALSE FALSE FALSE  TRUE  TRUE FALSE

str_starts(x2,"T")
[1]  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE

str_ends(x2,"e")
[1]  TRUE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE

x2
[1] "The"     "birch"   "canoe"   "slid"    "on"      "the"    "smooth"  "planks."

str_replace(x2,"o","A")
[1] "The"     "birch"   "canAe"   "slid"    "An"      "the"    "smAoth"  "planks."

str_replace_all(x2,"o","A")
[1] "The"     "birch"   "canAe"   "slid"    "An"      "the"    

[7] "smAAth"  "planks."

x
[1]"The birch canoe slid on the smooth planks."

str_remove(x," ")
[1] "Thebirch canoe slid on the smooth planks."

str_remove_all(x," ")
[1] "Thebirchcanoeslidonthesmoothplanks."

arrange()
test = iris
arrange(test,Sepal.Length)

arrange(test,desc(Sepal.Length))
#按降序

distinct(test, Species, .keep)

x 
apply(x,1,sum)

load("test2.Rdata")
apply(test,1,var)

sort(apply(test,1,var))

tail(sort(apply(test,1,var)),1000)

lapply

sapply