title: Merging Dataframes but losing Data
body: <p>I have two dataframes. Dataframe A has 5 columns (the first one being tickers) and Dataframe B has 2 columns (the first one being tickers). They are of different lengths. I am trying to add a 6th column to dataframe A based on matching the tickers. Not all the tickers are in dataframe B and when using the merge function I am losing those tickers. How do I keep all the data I already have in dataframe A and add a column, perhaps filling the space where the ticker is not found in dataframe B with NaN.</p>