> rm(list=ls())
> 
> 
> # 聚合函式學習
> data(iris)
> ##tapply 分組求和
> (aa<-tapply(iris$Sepal.Length,iris$Species,sum))
    setosa versicolor  virginica 
     250.3      296.8      329.4 
> 
> ##rowsum  分組求和
> (bb<-rowsum(iris[,c(1,2,3,4)],group=iris$Species))
           Sepal.Length Sepal.Width Petal.Length Petal.Width
 

setosa            250.3       171.4         73.1        12.3
versicolor        296.8       138.5        213.0        66.3
virginica         329.4       148.7        277.6       101.3
> 
> 
> ##aggregate 分組求和
> 
> (cc<-aggregate(iris[,c(1,2,3,4)],by=list(iris[,5]),sum))
     Group.1 Sepal.Length Sepal.Width Petal.Length Petal.Width
 

1     setosa        250.3       171.4         73.1        12.3
2 versicolor        296.8       138.5        213.0        66.3
3  virginica        329.4       148.7        277.6       101.3
> 
> 
> ##tabulate  計數
> (dd<-tabulate(iris$Species))
[1] 50 50 50
> 
> ## table  計數
> (ee<-table(iris$Species))
 


    setosa versicolor  virginica 
        50         50         50 
> 
> 
> ## xtabls 計數
> (ff<-xtabs(~Species,iris))
Species
    setosa versicolor  virginica 
        50         50         50 
> 
> 
> 
> 
> ##查詢是否有重複項
> a101<-c(1,2,3,3,4,5,6,7)
> (a102<-duplicated(a101))
[1] FALSE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE
>