NOx Air Pollution Data

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

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")


# \donttest{
## These examples take too much time and are not run during testing
## p = 340  ==> already Least Squares is not fast
if (FALSE) {
  (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))
}
# }