NOx Air Pollution Data

Description

A typical medium sized environmental data set with hourly measurements of NOx pollution content in the ambient air.

Usage

data(NOxEmissions, package="robustbase")

Format

A data frame with 8088 observations on the following 4 variables.

julday

day number, a factor with levels 373 ... 730, typically with 24 hourly measurements.

LNOx

\log of hourly mean of NOx concentration in ambient air [ppb] next to a highly frequented motorway.

LNOxEm

\log of hourly sum of NOx emission of cars on this motorway in arbitrary units.

sqrtWS

Square root of wind speed [m/s].

Details

The original data set had more observations, but with missing values. Here, all cases with missing values were omitted (na.omit(.)), and then only those were retained that belonged to days with at least 20 (fully) observed hourly measurements.

Source

René Locher (at ZHAW, Switzerland).

See Also

another NOx dataset, ambientNOxCH.

Examples

data(NOxEmissions)
plot(LNOx ~ LNOxEm, data = NOxEmissions, cex = 0.25, col = "gray30")

## Not run: ## these take too much time --
 ## p = 340  ==> already Least Squares is not fast
 (lmNOx <- lm(LNOx ~ . ,data = NOxEmissions))
 plot(lmNOx) #->  indication of 1 outlier

 M.NOx <- MASS::rlm(LNOx ~ . , data = NOxEmissions)
 ## M-estimation works
 ## whereas  MM-estimation fails:
 try(MM.NOx <- MASS::rlm(LNOx ~ . , data = NOxEmissions, method = "MM"))
 ## namely because S-estimation fails:
 try(lts.NOx <- ltsReg(LNOx ~ . , data = NOxEmissions))
 try(lmR.NOx <- lmrob (LNOx ~ . , data = NOxEmissions))

## End(Not run)