R语言因子序列的创建

R语言因子序列的创建

使用gl函数可以方便地创建一个因子向量。其基本形式为：

gl
（n, k, length = n*k, labels = 1:n, ordered = FALSE
）

相应的示例代码如下：

gl(3,4,labels=c("one","two","three"))
  [1] one   one   one   one   two   two   two   two   three three three three
    Levels: one two three
gl(3,2,length=12,labels=c("one","two","three"))
  [1] one   one   two   two   three three one   one   two   two   three three
    Levels: one two three

在上例中，gl（3,4,labels=c（"one","two","three"））可以理解为：产生一个因子水平为"one","two","three"的无序因子向量，其中每个水平连续重复4次。

gl（3,2,12,labels=c（"one","two","three"））则可以理解为：每个水平连续重复了两次产生“one one two two three three”，而后该序列又重复了一次（直至向量长度为12为止）。