R group by date, and summarize the values

Question

R is new for me and I am working with a (private) data set.

I have the following problem, I have a lot of time series:

2015-04-27  12:29:48
2015-04-         


        

Answer 1

using data.table

Test$Datetime <- as.Date(Test$Datetime)
DT<- data.table(Test )
DT[,sum(value),by = Datetime]

     Datetime   V1
1: 2015-04-27 46.1
2: 2015-04-28  3.0