如何找到每个类别中价格涨幅最大的十大产品

Question

我刚开始学习使用R.如何在每个产品类别中找到每月价格涨幅最大的十大产品？

Answer 1

如果你可以使用包dplyr：

library(dplyr)
df <- read.table(text="
Category, Product, PrevMonthPrice, CurrentMonthPrice
Food,Orange,5,10
Clothing,Shirt,25,35
Food,Apple,2,4
Clothing,Hat,25,15
Food,Soup,4.5,3
Clothing,Coat,150,200
Food,Meat,9,11
Clothing,Scarf,20,25
Food,Rice,8,12
Clothing,Shoes,150,125", sep=",", header=TRUE)

df %>% 
        mutate(increase=CurrentMonthPrice-PrevMonthPrice) %>% 
        group_by(Category) %>%
        arrange(-increase) %>% 
        top_n(2)


Source: local data frame [4 x 5]
Groups: Category [2]

  Category Product PrevMonthPrice CurrentMonthPrice increase
    (fctr)  (fctr)          (dbl)             (int)    (dbl)
1 Clothing    Coat            150               200       50
2 Clothing   Shirt             25                35       10
3     Food  Orange              5                10        5
4     Food    Rice              8                12        4

Answer 2

您可以使用＆＃34; pure＆＃34;获得相同的结果R：

df$increase=df$CurrentMonthPrice-df$PrevMonthPrice
top=2
res=lapply(split(df,df$Category), function(xd){
  xd[with(xd,order(-increase)),][1:top,]
})

do.call(rbind,res)