读入函数，根据数据格式的选择函数：

    1. # .txt file: Read tab separated values 
    2. my_data <- read.delim(file.choose()) 
    3. # .csv file: Read comma (",") separated values 
    4. my_data <- read.csv(file.choose()) 
    5. # .csv file: Read semicolon (";") separated values 
    6. my_data <- read.csv2(file.choose())
    9.  genus = read.csv("./input/abundance/relative_abundance/genus.csv",
    10.                    header = T,row.names = 1)
    12. genus = read.table("./input/abundance/relative_abundance/genus.xls",
    13.                   sep = "\t",header = T,row.names = 1)
    15. KEGG_L3 <- read.xlsx("./input/KEGG_L3.xlsx", sheetIndex = 1)