画图神器ggplot2之一：geom_point

p <- ggplot(mtcars, aes(wt, mpg))
p + geom_point()
# Add aesthetic mappings
p + geom_point(aes(colour = qsec))
p + geom_point(aes(alpha = qsec))
p + geom_point(aes(colour = factor(cyl)))
p + geom_point(aes(shape = factor(cyl)))
p + geom_point(aes(size = qsec))
# Change scales
p + geom_point(aes(colour = cyl)) + scale_colour_gradient(low = "blue")
p + geom_point(aes(size = qsec)) + scale_area()scale_area is deprecated. Use scale_size_area instead.
  Note that the behavior of scale_size_area is slightly different:
  by default it makes the area proportional to the numeric value. (Deprecated; last used in version 0.9.2)
p + geom_point(aes(shape = factor(cyl))) + scale_shape(solid = FALSE)
# Set aesthetics to fixed value
p + geom_point(colour = "red", size = 3)
qplot(wt, mpg, data = mtcars, colour = I("red"), size = I(3))
# Varying alpha is useful for large datasets
d <- ggplot(diamonds, aes(carat, price))
d + geom_point(alpha = 1/10)
d + geom_point(alpha = 1/20)
d + geom_point(alpha = 1/100)
# You can create interesting shapes by layering multiple points of
# different sizes
p <- ggplot(mtcars, aes(mpg, wt))
p + geom_point(colour="grey50", size = 4) + geom_point(aes(colour = cyl))
p + aes(shape = factor(cyl)) +
  geom_point(aes(colour = factor(cyl)), size = 4) +
  geom_point(colour="grey90", size = 1.5)
p + geom_point(colour="black", size = 4.5) +
  geom_point(colour="pink", size = 4) +
  geom_point(aes(shape = factor(cyl)))
# These extra layers don't usually appear in the legend, but we can
# force their inclusion
p + geom_point(colour="black", size = 4.5, show_guide = TRUE) +
  geom_point(colour="pink", size = 4, show_guide = TRUE) +
  geom_point(aes(shape = factor(cyl)))
# Transparent points:
qplot(mpg, wt, data = mtcars, size = I(5), alpha = I(0.2))
# geom_point warns when missing values have been dropped from the data set
# and not plotted, you can turn this off by setting na.rm = TRUE
mtcars2 <- transform(mtcars, mpg = ifelse(runif(32) < 0.2, NA, mpg))
qplot(wt, mpg, data = mtcars2)Warning message:
Removed 11 rows containing missing values (geom_point).
qplot(wt, mpg, data = mtcars2, na.rm = TRUE)
# Use qplot instead
qplot(wt, mpg, data = mtcars)
qplot(wt, mpg, data = mtcars, colour = factor(cyl))
qplot(wt, mpg, data = mtcars, colour = I("red"))