Introduction

The RAQSAPI package for the R programming environment allows a R programming environment to connect to and retrieve data from the United States Environmental Protection Agency’s (US EPA) Air Quality System (AQS) Data Mart API v2 Air Quality System[@AQSDataMartWelcome] interface directly. This package enables the data user to omit legacy challenges including coercing data from a JSON object to a usable R object, retrieving multiple years of data, formatting API requests, retrieving results, handling credentials, requesting multiple pollutant data and rate limiting data requests. All the basic functionality of the API have been implemented that are available from the AQS API Data Mart server. The library connects to AQS Data Mart API via Hypertext Transfer Protocol (HTTP) so there is no need to install external ODBC drivers, configure ODBC connections or deal with the security vulnerabilities associated with them. Most functions have a parameter, return_header which by default is set to FALSE. If the user decides to set return_header to TRUE, then that function will return a R AQS_DATAMART_APIv2 S3 object which is a two item named list.
The first item, ($Header) in the AQS_DATAMART_APIv2 object is a tibble[@package:tibble] which contains the header information. The Header contains status information regarding the request (success/fail), any applicable error messages returned from the API, if any exist, the URL used in the request, a date and time stamp noting when request was received and other useful information. The second item of the AQS_DATAMART_APIv2 object ($Data) is a tibble which contains the actual data being requested. For functions with the return_header option set to FALSE (default) a simple tibble is returned with just the $Data portion of the request. After each call to the API a five second stall is invoked to help prevent overloading the Data Mart API server and to serve as a simple rate limit. ¹