How to filter or subset specific date and time intervals in R? Lubridate?

问题

I have a dataset consisting of two columns. A datetime column and a column with numerical values. Its a simple dataset, so I did not attach it..

What I need to do, is to filter or subset the data corresponding with a class schedule, so that I get a dataset/dataframe with datetime values and numerical values for the time when the class has lectures only.

The class schedule is different from each day of the week, e.g. Mondays 8:00-9.50, 10.30-11.30, 14.50-15:50. Tuesdays 10.30-11.30, 14.10-15.30, Wednesdays...an so on.

Any idea how I could do this?

I usually convert datetime-values to POSIXct format, but recently I read about lubridate.

I am just still not sure how to efficiently subset with all these criteria.

Perhaps I should subset the data according to the weekdays first. And then subset the different weekdays according to the lecture time...

Hope someone can help me.

BTW: The data is for all of 2014, so I actually have to avoid the data when the class have holidays as well...

回答1:

Convert class intervals to an interval class in lubridate. Then subset based on the test of if the dates are in the intervals...

> a <- new_interval(Sys.time(), Sys.time() + 120)
> Sys.time() %within% a
[1] TRUE

回答2:

I will try this, where the D$Time is in POSIXct format:

# Create column with weekday
D$Weekday <- D$Time
D$Weekday <- weekdays(as.Date(D$Time))

# Subset weekdays
MO <- subset(D, D$Weekday == "Monday")
head(MO)
TU <- subset(D, D$Weekday == "Tuesday")
WE <- subset(D, D$Weekday == "Wednesday")
MO <- subset(D, D$Weekday == "Thursday")
MO <- subset(D, D$Weekday == "Friday")
MO <- subset(D, D$Weekday == "Saturday")

# Subset lecture of weekday
MO_L1 <- subset(MO, format(MO$Time, "%H:%M:$S") > "07:55:00" &
              format(MO$Time, "%H:%M:$S") < "09:30:00")
head(MO_L1)
tail(MO_L1)
MO_L2 <- subset(MO, format(MO$Time, "%H:%M:$S") > "10:55:00" &
              format(MO$Time, "%H:%M:$S") < "11:30:00")

And in the end combine all the subset to a new dataset...

来源：https://stackoverflow.com/questions/30516157/how-to-filter-or-subset-specific-date-and-time-intervals-in-r-lubridate

标签

datetime

filtering

posixct

lubridate