README

Use this package to import official U.S. air quality data from AirData into R. Seeking comment!

Installation

Install directly from GitHub using devtools:

if (!require("devtools")) install.packages("devtools")
library("devtools")
install_github("airdata", "holstius")

Example usage

A typical query might start with a pollutant of interest. Here's how to identify the parameter code for such a pollutant:

# Fetch all existing parameter codes
params <- AQDMRS.list(name="param")

# Find just the one(s) corresponding to a search phrase
library(stringr)
phrase <- "black carbon"
show(subset(params, str_detect(tolower(name), phrase)))

There are two such codes. LC (88313) means "local conditions" and STP (84313) means "standard temperature and pressure". You can use either, although a particular site might record data for only one of the two. In this case, STP is what we want.

Before executing a query, you'll need an AirData username and password. Then you can do the following:

# If you don't supply user="..." and pw="...", you'll be prompted
q <- AQDMRS.query(
    state = "06",           # California
    county = "001",         # Alameda County
    site = "0011",          # West Oakland site
    bdate = "2012-04-15",   
    edate = "2012-04-23",
    param = "84313"
)
BC_STP <- eval(q)

Queries are lazy and can me modified before being evaluated, or recycled after evaluation. This is handy, because you don't have to type common parameters more than once:

q$param <- "88313"
BC_LC <- eval(q)

And, if you like, you can specify user=... and pw=... in the query, rather than entering them interactively.

A quick time-series plot:

with(BC_STP, plot(GMT, value, main="West Oakland BC", ylab="ug/m3 (STP)"))

Windows support

AirData has an annoying habit of appending END OF FILE to every dataset. On unix-compatible platforms, including OS X, it's fast and easy to eliminate this with a quick call to grep. On Windows, there's no builtin grep, and there's no fast workaround in R (AFAIK, but please comment if you know of one). A workaround (and you can do this on other platforms, too) is:

1. download a .txt file from the AirData website (choose "DMCSV" for the format)
2. open it up in a text editor, delete the "END OF FILE" line, and re-save

Then you can import the file into R with read.DMCSV():

library(airdata)
downloaded_file <- file.choose() 
BC_STP <- read.DMCSV(downloaded_file, omit.EOF=FALSE)

More demos

demo("criteria", package="airdata")
demo("black_carbon", package="airdata")