R语言提取信息修改每一列的字符串

请问怎么用R代码把矩阵里type改成“control”和“tumor”两种分类，Sex列改成“Female”和“Male”，Grade改成I到IV级这些。能力有限，只能改动一列，不能批次改3列。谢谢各位帮忙解答

这是我改Type的代码

其实你这里就三列，可以一次一次替换都行，而且都是分类变量甚至直接用查找替换都可以。for循环也可以，思路简单。不过用ifelse和apply函数可以高class点，替换掉ABCD即可

> data <- matrix(c("A", "B", "A", "C", "C", "D"), nrow = 3, ncol = 2)
> data
     [,1] [,2]
[1,] "A"  "C" 
[2,] "B"  "C" 
[3,] "A"  "D" 
> data <- apply(data, 2, function(x) {
+   ifelse(x == "A", "Male", ifelse(x == "B", "Female", ifelse(x == "C", "tumor", "control")))
+ })
> data
     [,1]     [,2]     
[1,] "Male"   "tumor"  
[2,] "Female" "tumor"  
[3,] "Male"   "control"