+----------------+-------------------+
| NOxEmissions   | R Documentation   |
+----------------+-------------------+

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)

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
~~~~~~

RenÃ© 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)

