title: R: How to create a data frame with one observation for each combination of factors
body: <p>I hope all is well. I am writing with regards to a very specific question in R to which I so far was not able to find a solution online. If the question has already been addressed somewhere else, I am sorry for bothering you but would appreciate if you could provide me with the link.</p>
  
  <p>I have 3 separate data sets:</p>
  
  <p>The first one is a list of companies. The second one is a list of years. The third one is a list of countries.</p>
  
  <p>My objective is now to merge these 3 data sets into a new data frame. The final data frame should create <strong>a data row for each combination of these 3 variables</strong>. This is the reason why I cannot use the merge() function. As a next step, I want to match data along this newly created data frame.</p>
  
  <p>Thank you ever you much for your support - and again sorry if the question has already been addressed elsewhere!</p>