R - 在一个间隔上汇总data.frame

Question

我试图在每个星期五对data.frame求一个变量。

随机数据框

mydf = data.frame(      "ID"   = c( rep( "A" , 6) , rep( "B" , 5 ) ),   "Date" = c( "2017-09-08","2017-09-10","2017-09-13","2017-09-15","2017-09-20","2017-09-22","2017-08-03","2017-08-04","2017-08-10","2017-08-11","2017-08-12" , "Var"  = c( 1,2,3,4,5,6,7,8,NA,10,11) )

mydf$Date = as.Date( mydf$Date )

mydf = cbind( mydf , "WeekDay" = weekdays( mydf$Date ) )

我想得到什么

df_ToGet = 
data.frame( 
    "ID"   = c( rep( "A" , 3) , rep( "B" , 2 ) ),
    "Date" = c( "2017-09-08","2017-09-15","2017-09-22","2017-08-04","2017-08-11"  ),
    "Var_Sum"  = c( 1 , 9 , 11 , 15, 10 )
    )

我尝试了什么

我考虑过使用 dplyr :: summarize 和聚合，但我不知道如何正确设置 by 条件。

mydf %>% group_by( ID ) %>% summarize( Var_Sum = aggregate( Var , sum ,  by=list ( (mydf$Weekday)=="Friday") )  )

我已经看到使用 cut 函数解决了一些类似的问题，但这似乎是将条件设置为标准周？我还不熟悉它。

Answer 1

我们需要使用Fragment

创建分组变量

cumsum