robustbase (version 0.5-0-1)

ambientNOxCH: Daily Means of NOx (mono-nitrogen oxides) in air

Description

This dataset contains daily means (from midnight to midnight) of NOx, i.e., mono-nitrogen oxides, in [ppb] at 13 sites in central Switzerland and Aarau for the year 2004.

Usage

data(ambientNOxCH)

encoding

latin1

source

http://www.in-luft.ch/ http://www.empa.ch/plugin/template/empa/*/6794 http://www.bafu.admin.ch/umweltbeobachtung/02272/02280

Details

The 13 sites are part of one of the three air quality monitoring networks: inLuft (regional authorities of central Switzerland and canton Aargau) NABEL (Swiss federal network) MFM-U (Monitoring flankierende Massnahmen Umwelt), special Swiss federal network along transit motorways A2 and A13 from Germany to Italy through Switzerland The information within the brackets means: Swiss coordinates km east, km north; m above sea level; network When the measuring sites are exposed to the same atmospheric condition and when there is no singular emission event at any site, log(mean(NOx) of a specific day at each site) is a linear function of log(yearly.mean(NOx) at the corresponding site). The offset and the slope of the straight line reflects the atmospheric conditions at this specific day. During winter time, often an inversion prevents the emissions from being diluted vertically, so that there evolve two separate atmospheric compartements: One below the inversion boundary with polluted air and one above with relatively clean air. In our example below, Rigi Seebodenalp is above the inversion boundary between December 10th and 12th.

See Also

another NOx dataset, NOxEmissions.

Examples

data(ambientNOxCH)
str (ambientNOxCH)

yearly <- log(colMeans(ambientNOxCH[,-1], na.rm=TRUE))
xlim <- range(yearly)
lNOx <- log(ambientNOxCH[, -1])
days <-     ambientNOxCH[, "date"]

## Subset of 9 days starting at April 4:
idays <- seq(which(ambientNOxCH$date=="2004-12-04"), length=9)
ylim <- range(lNOx[idays,],na.rm=TRUE)
op <- par(mfrow=c(3,3),mar=rep(1,4), oma = c(0,0,2,0))

for (id in idays) {
  daily <- unlist(lNOx[id,])
  plot(NA, xlim=xlim,ylim=ylim, ann=FALSE, type = "n")
  abline(0:1, col="light gray")
  abline(lmrob(daily~yearly, na.action=na.exclude),
         col="red", lwd=2)
  text(yearly, daily, names(yearly), col="blue")
  mtext(days[id], side=1, line=-1.2, cex=.75, adj=.98)
}
mtext("Daily ~ Yearly  log( NOx mean values ) at 13 Swiss locations",
      outer=TRUE)
par(op)

## do all 366 regressions:  Least Squares and Robust:
LS <- lapply(1:nrow(ambientNOxCH), function(id)
             lm(unlist(lNOx[id,]) ~ yearly,
                na.action = na.exclude))
R <- lapply(1:nrow(ambientNOxCH),
            function(id) lmrob(unlist(lNOx[id,]) ~ yearly,
                               na.action = na.exclude))
## currently 4 warnings about non-convergence;
## which ones?
days[notOk <- ! sapply(R, `[[`, "converged") ]
## "2004-01-10" "2004-05-12" "2004-05-16" "2004-11-16"

## first problematic case:
daily <- unlist(lNOx[which(notOk)[1],])
plot(daily ~ yearly,
     main = paste("lmrob() non-convergent:",days[notOk[1]]))
rr <- lmrob(daily ~ yearly, na.action = na.exclude,
            control = lmrob.control(trace=3, max.it = 100))
##-> 53 iter.

## Look at all coefficients:
R.cf <- t(sapply(R, coef))
C.cf <- t(sapply(LS, coef))
plot(C.cf, xlim=range(C.cf[,1],R.cf[,1]),
           ylim=range(C.cf[,2],R.cf[,2]))
mD1 <- rowMeans(abs(C.cf - R.cf))
lrg <- mD1 > quantile(mD1, 0.80)
arrows(C.cf[lrg,1], C.cf[lrg,2],
       R.cf[lrg,1], R.cf[lrg,2], length=.1, col="light gray")
points(R.cf, col=2)

## All robustness weights
aW <- t(sapply(R, weights))
colnames(aW) <- names(yearly)
summary(aW)
sort(colSums(aW < 0.05, na.rm = TRUE)) # how often "clear outlier":
# lu st zg ba se sz su si re la ef ad ri
#  0  0  0  1  1  1  2  3  4 10 14 17 48

lattice::levelplot(aW, asp=1/2, main="Robustness weights",
                   xlab= "day", ylab= "site")