I currently have a dataset that contains multiple of the same values for a variable (industry_code) in different areas (different values of the variable area_flips) and for different codes (agglvl_code) with quarterly data. I want to narrow this to achieve just the 4 quarterly values for each industry code (so a total of all the areas and agglvl_codes for a single industry_code but whilst keeping quarterly observations and other variables for each quarter).