# 基础作图法绘制火山高度数据颜色图
data(volcano)
par(mar = rep(0, 4), ann = FALSE)
x = 10 * (1:nrow(volcano))
y = 10 * (1:ncol(volcano))
image(x, y, volcano, col = terrain.colors(100), axes = FALSE)
contour(x, y, volcano, levels = seq(90, 200, by = 5),
        add = TRUE, col = "peru")
box()
