2.1 简介
qplot的意思是快速作图（quick plot）。
qplot是一种快捷方式，如果您已习惯于使用基础plot()，则可以使用它。它可以使用一致的调用模式快速创建许多不同类型的图。
qplot(x, y, ..., data, facets = NULL, margins = FALSE, geom = "auto", xlim = c(NA, NA), ylim = c(NA, NA), log = "", main = NULL, xlab = NULL, ylab = NULL, asp = NA, stat = NULL, position = NULL)
2.2 数据集
> head(diamonds) # A tibble: 6 x 10 carat cut color clarity depth table price x y z <dbl> <ord> <ord> <ord> <dbl> <dbl> <int> <dbl> <dbl> <dbl> 1 0.23 Ideal E SI2 61.5 55 326 3.95 3.98 2.43 2 0.21 Premium E SI1 59.8 61 326 3.89 3.84 2.31 3 0.23 Good E VS1 56.9 65 327 4.05 4.07 2.31 4 0.290 Premium I VS2 62.4 58 334 4.2 4.23 2.63 5 0.31 Good J SI2 63.3 58 335 4.34 4.35 2.75 6 0.24 Very Good J VVS2 62.8 57 336 3.94 3.96 2.48
A dataset containing the prices and other attributes of almost 54,000 diamonds. The variables are as follows:
- price: price in US dollars (\$326–\$18,823)
- carat: weight of the diamond (0.2–5.01)
- cut: quality of the cut (Fair, Good, Very Good, Premium, Ideal)(均匀、良好、非常好、优质、理想)
- color: diamond colour, from D (best) to J (worst)
- clarity: a measurement of how clear the diamond is (I1 (worst), SI2, SI1, VS2, VS1, VVS2, VVS1, IF (best))
- x: length in mm (0–10.74)
- y: width in mm (0–58.9)
- z: depth in mm (0–31.8)
- depth: total depth percentage = z / mean(x, y) = 2 * z / (x + y) (43–79)
- table: width of top of diamond relative to widest point (43–95)
抽样：
set.seed(1410) # 让样本可重复 dsmall <- diamonds[sample(nrow(diamonds), 100), ]