title: Merging two rows with some having missing values in R
body: <p>I would like to ask the R community how to merge two rows with the same ID (i.e. same participant) with some variables that are identical and others where there are NA's. In my example, I would like all the values 4-5-6 to appear on one row and therefore for the NA's (or empty cells) to be gone.</p>
  
  <p><img src="https://i.stack.imgur.com/EcBs8.png" alt="This is an example of what my data looks like"></p>
  
  <p>I have tried using dplyr without much success, and I have to do the merging by hand (which is quite time consuming and increases the risk for errors). Thank you in advance for your help with this problem!</p>