new.values <- cbind(c(0, 1, 2, 3, 4, 5, 6, 7, 8), c(NA, NA, 1, NA, 2, NA, NA, NA, NA))
new.r <- reclassify(r, rcl=new.values)

test.edge <- rasterToPolygons(clump(new.r), dissolve=TRUE)
plot(test.edge, add=TRUE)