操作矩阵每行元素| R Programming for Bioi

最近在看这本书：https://www.amazon.com/Programming-Bioinformatics-Chapman-Computer-Analysis/dp/1420063677
其中有一道习题

Write an R function that takes a matrix as input and standardizes each row
by subtracting the median and dividing by the MAD. You might want to look
at the functions mad and median. Next, generalize your function so that these
are the default values, but allow the user to select other measures of the center
and spread, should they want to use them.

就是要把矩阵的每行元素都减去median然后除以mad值
然后把这两个函数作为默认，允许用户自己输入函数来计算

set.seed(123)
a <- matrix(sample(1:20,12),ncol = 3)
a
f1 <- function(x) {
    median_row <- apply(x,1,median)
    mad_row <- apply(x,1,mad)
    x <- sweep(sweep(x,1,median_row),1,FUN = "/",mad_row)
    return(x)
}
f1(a)

# generalized
f1 <- function(x, 
               sub_fun = "median", 
               divid_fun = "mad") {
    median_row <- apply(x,1,sub_fun)
    mad_row <- apply(x,1,divid_fun)
    x <- sweep(sweep(x,1,median_row),1,FUN = "/",mad_row)
    return(x)
}

f1(a)

用到了sweep函数