Satellite Radar Image Data from near Munich

Description

The data were supplied by A. Frery. They are a part of a synthetic aperture satellite radar image corresponding to a suburb of Munich. Provided are coordinates and values corresponding to three frequency bands for each of 1573 pixels.

Usage

data(radarImage, package="robustbase")

Format

A data frame with 1573 observations on the following 5 variables.

X.coord

a numeric vector

Y.coord

a numeric vector

Band.1

a numeric vector

Band.2

a numeric vector

Band.3

a numeric vector

Source

The website accompanying the MMY-book: https://www.wiley.com/legacy/wileychi/robust_statistics/

Examples

data(radarImage)
plot(Y.coord ~ X.coord, data = radarImage)

## The 8 "clear" outliers (see also below)
ii8 <- c(1548:1549, 1553:1554, 1565:1566, 1570:1571)
outF <- 1+(seq_len(nrow(radarImage)) %in% ii8)
pairs(radarImage[, 3:5], main = "radarImage (n = 1573)",
      col = outF, pch=outF)

## Finding outliers -----------------------------------------

set.seed(1)
system.time(cc.ri <- covMcd(radarImage))# ~ 0.1 sec
## check for covMcd() consistency:
iiO <- as.integer(
 c(262, 450:451, 480:481, 509, 535, 542, 597, 643, 669, 697, 803:804, 832:834,
   862:864, 892, 989, 1123, 1145, 1223:1224, 1232:1233, 1249:1250, 1267, 1303,
   1347, 1357, 1375, 1411, 1419:1420, 1443, 1453, 1504, 1510:1512,
   1518:1521, 1525:1526, 1543:1544, 1546:1555, 1557:1558, 1561:1562, 1564:1566,
   1569:1571, 1573))
length(iiO) # 73 -- other seeds sometimes give 72, rarely 71 "outliers"
table(isO <- cc.ri$mcd.wt == 0) # 2023-05: 118
stopifnot(exprs = {
    ## identical(iiO, which(isO)) -- TRUE before 2023-05  covMcd() change
    ii8 %in% which(isO) # ii8 is subset of isO
    identical(ii8, which(cc.ri$mah > 200))
    length(intersect(cc.ri$best, iiO)) == 0
})

cc <- c(adjustcolor("black", 0.4), adjustcolor("tomato", 0.8))
pairs(radarImage, main = "radarImage (n = 1573) + Outliers", gap=0,
      col = cc[1+isO], pch = c(1,8)[1+isO], cex = 0.8)