title: How to filter or subset specific date and time intervals in R? Lubridate?
body: <p>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..</p>
  
  <p>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 <strong>for the time when the class has lectures</strong> only.</p>
  
  <p>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.</p>
  
  <p>Any idea how I could do this?</p>
  
  <p>I usually convert datetime-values to POSIXct format, but recently I read about lubridate.</p>
  
  <p>I am just still not sure how to efficiently subset with all these criteria.</p>
  
  <p>Perhaps I should subset the data according to the weekdays first.
  And then subset the different weekdays according to the lecture time...</p>
  
  <p>Hope someone can help me.</p>
  
  <p>BTW: The data is for all of 2014, so I actually have to avoid the data when the class have holidays as well...</p>