I often want to quickly create a lag or lead variable in an R data frame. Sometimes I also want to create the lag or lead variable for different groups in a data frame, for example, if I want to lag GDP for each country in a data frame. I've found the various R methods for doing this hard to remember and usually need to look at old blog posts . Any time we find ourselves using the same series of codes over and over, it's probably time to put them into a function. So, I added a new command– slide –to the DataCombine R package (v0.1.5). Building on the shift function TszKin Julian posted on his blog , slide allows you to slide a variable up by any time unit to create a lead or down to create a lag. It returns the lag/lead variable to a new column in your data frame. It works with both data that has one observed unit and with time-series cross-sectional data. Note: your data needs to be in ascending time order with equally spaced time increments. For example 1995, 1996
Comments
Do you have any suggestions to how one can delay the code with x seconds? When using the code for retrieving many pages from same server I am overloading the server giving me "bad" files with no text, and probably some angry hosts, which is not my intention.
I solved the problem by taking 5% of total n of pages at the time. Therefore i believe a solution would be if one could make count total number of pages in the input file and tell the code to only send like 50 requests or 5% of total n at the time.
Best
Kasper
install.packages("Rcrawler")
see manual for more detail here R web scraper