Scatter Plot Matrices

lattice包提供了很多画图函数，这儿我们使用lattice包splom()画散点矩阵图和parallelplot()画平行坐标图；

记得有一次帮别人画基因cluster随时间表达模式图；每个基因在各个时刻表达值使用一条折线表示，当时使用了循环一条线一条线的画；现在可以使用parallelplot()这个函数；

Draw Conditional Scatter Plot Matrices and Parallel Coordinate Plots

Usage
splom(x, data, ...)
parallelplot(x, data, ...)

x: 可以是表达式，也可以是data.frame；
表达式格式：~ x | g1 * g2 ；x可以是数据框或者矩阵；g1，g2是数据因子；展示g1 * g2 各水平组合下，x中各数据分布情况；
group: 选择分组的因子

library(lattice)

super.sym <- trellis.par.get("superpose.symbol")
splom(~iris[1:4], groups = Species, data = iris,
      panel = panel.superpose,
      key = list(title = "Three Varieties of Iris",
                 columns = 3, 
                 points = list(pch = super.sym$pch[1:3],
                               col = super.sym$col[1:3]),
                 text = list(c("Setosa", "Versicolor", "Virginica"))))

splom(~iris[1:3]|Species, data = iris, 
      layout=c(2,2), pscales = 0,
      varnames = c("Sepal\nLength", "Sepal\nWidth", "Petal\nLength"),
      page = function(...) {
        ltext(x = seq(.6, .8, length.out = 4), 
              y = seq(.9, .6, length.out = 4), 
              labels = c("Three", "Varieties", "of", "Iris"),
              cex = 2)
      })

parallelplot(~iris[1:4] | Species, iris) 

parallelplot(~iris[1:4], iris, groups = Species,
             horizontal.axis = FALSE, scales = list(x = list(rot = 90)))