R Macro with Iteration through URL : Having a problem creating a macro variable within an API call in R. I am trying to loop through a vector of zip codes and make an API call on that vector iteratively. Pretty unfamiliar with iterating through a R list that needs to be macro'd out.

Familiar with sas macros where I'd 

Here is my code:

#creating a dataframe of 10 sample California zip codes to iterate through from database
zip_iterations<-sqlQuery(ch,"Select distinct zip from zip_codes where state='CA' limit 10",believeNRows="F")


#Calling the api to retrieve the JSON
json_file <- "http://api.openweathermap.org/data/2.5/weather?zip=**'MACRO VECTOR TO ITERATE'**     

My goal is to go through the list of 10 zip codes in the dataframe by using a macro.

Thanks

       