```
# NOT RUN {
x <- c(1, 1, 3, 3, 1)
y <- c(1, 3, 3, 1, 1)
polyarea(x, y)
polyarea(cbind(x, x), cbind(y, y)) ## c(4, 4)
polyarea(cbind(x, x), cbind(y,y), 1) ## c(4, 4)
polyarea(rbind(x, x), rbind(y,y), 2) ## c(4, 4)
# }
```

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