Aggregate data to weekly level with every week starting from Monday

Question

I have a data frame like,

2015-01-30     1       Fri
2015-01-30     2       Sat
2015-02-01     3       Sun
2015-02-02     1       Mon
2015-02-03     1       Tue
2015-02-04     1       Wed 
2015-02-05     1       Thu
2015-02-06     1       Fri
2015-02-07     1       Sat
2015-02-08     1       Sun

I want to aggregaate it to weekly level such that every week starts from "monday" and ends in "sunday". So, in the aggregated data for above, first week should end on 2015-02-01.

output should look like something for above

firstweek    6  
secondweek   7

I tried this,

data <- as.xts(data$value,order.by=as.Date(data$interval))
weekly <- apply.weekly(data,sum)

But here in the final result, every week is starting from Sunday.

Answer 1

This should work. I've called the dataframe m and named the columns possibly different to yours.

library(plyr) # install.packages("plyr")

colnames(m) = c("Date", "count","Day")
start  = as.Date("2015-01-26")
m$Week <- floor(unclass(as.Date(m$Date) - as.Date(start)) / 7) + 1
m$Week = as.numeric(m$Week)
m %>% group_by(Week) %>% summarise(count = sum(count))

The library plyr is great for data manipulation, but it's just a rough hack to get the week number in.