Panel data set up

I have a 1101704 x 4 table with the following variables about solar panels:

• date (MM/yyyy) when the panel was installed
• zip code for where it was installed
• cost variables
• and the size of the panel (total capacity)

I'm trying to set this dataset up as a balanced panel by month across the years for which the data is available (Dec 2000 - May 2021). Some zip codes have multiple observations per month in a given year.

I know I need to group the data by zip code and MM/yyyy, but having issues with a groupsummary script...To group together I'm trying to aggregate/sum the capacity by zip code and month/year and then do a weighted average of cost and incentive based on the capacity for that given zip code and month/year. should this be done in a for loop? I need the final dataset to have rows for each month (12) for all years (2000-2021), and zip codes that do not have observations for that given month be assigned "-9999" value...

I'm pretty new to MatLab so any help with this would be greatly appreciated!!!

installation_date   zip         cost        incentive   total_capacity
'12/2000'	        11714	    10433.2	    3600	    1.2
'12/2000'	        11720	    10700	    3600	    1.2
'03/2001'       	11758	    15249	    5400	    1.8
'03/2001'       	11947	    35143.3 	13200	    4.4
'07/2001'       	11507	    23219	    6600	    2.2
'08/2001'	        11901	    21900	    7200	    2.4
'08/2001'	        11572	    21800	    7200	    2.4