Plotting Air Quality Egg data using R
I recently got an Air Quality Egg. The Air Quality Egg is a open source hardware project to measure air quality hyper-locally. My egg is located on the balcony of my flat in Brixton, London. The Air Quality Egg device has sensors which read NO2, CO, humidity & temperature and posts the data to Cosm. You can view readings and simple graphs on the Cosm feed page.
Air Quality Egg on the balcony of my flat
Plotting sensor data using R
I wanted to see the trends in the data so I wrote a script in R to curl the data from the Cosm API and plot it using GGPlot.
Here is the script:
| install.packages('RCurl') | |
| install.packages("ggplot2") | |
| library(ggplot2) | |
| library(RCurl) | |
| # grab an api key from cosm and put it here | |
| api_key = 'YOUR_API_KEY' | |
| # your feed id | |
| feed_id = '106267' | |
| csv_data = "" | |
| start_date = as.POSIXct("2013/05/07","GMT") | |
| end_date = as.POSIXct("2013/05/08","GMT") | |
| while (start_date < end_date) { | |
| start_date_as_str = format(start_date, format="%Y-%m-%dT%H:%M:00Z") | |
| next_date = start_date + (3 * 60 * 60) | |
| next_date_as_str = format(next_date, format="%Y-%m-%dT%H:%M:00Z") | |
| cosm_url = paste("http://api.cosm.com/v2/feeds/", feed_id, "/datastreams/NO2_00-04-a3-37-cc-cb_0.csv?start=", start_date_as_str, "&end=", next_date_as_str,"&interval=0", sep="") | |
| csv_data_for_period = getURL(cosm_url, httpheader = c('X-ApiKey' = api_key) ) | |
| csv_data = paste(csv_data, csv_data_for_period, "\n") | |
| start_date = next_date | |
| } | |
| data = read.table(textConnection(csv_data), sep = ",", col.names=c("at", "value")) | |
| data$timestamp <- strptime(data$at, "%FT%T", tz = "UTC") | |
| # strip out outliers | |
| data = data[which(data$value < 1000),] | |
| #summary(data) | |
| ggplot(data, aes(timestamp,value)) + geom_point() + geom_smooth() + xlab("Time") + ylab("NO2 PPB") |
Here are some example graphs of NO2 over a single day and several days. (Note I don’t have the latest sensor updates so the readings may be a bit off)
Plot of NO2 for a single day
Plot of NO2 for a 4 day period
