⭐️⭐️⭐️⭐️⭐️（实战前准备）

本文图片、代码取自生信技能树培训班。感谢各位老师的教学与前期工作准备。

一、将表格文件读入——生成数据框（PS：表格文件读入R，生成数据框，对数据框修改不会同步到表格文件），不要取原文件同名变量，以免覆盖原文件

1、常见表格文件后缀——csv（纯文本文件后缀无意义 ）

（1）可使用sublime打开——推荐

（2）使用R语言读取——可赋值（注意读取后格式是否是我们想要的），read函数(常规）与rio包(新手、懒人友好型⭐️⭐️⭐️）

  1. ex1 = read.table("ex1.txt") #读取txt格式文件
  2. ex1=read.table("ex1.txt",header = T)
  4. ex2 = read.csv("ex1.txt") #读取csv文件
  5. ex2=read.csv("ex2.csv",
  6.              row.names = 1,
  7.              check.names = F)
  9. #懒人必备读取/导出包“rio”⭐️⭐️⭐️
  10. #import()
  11. x <- import("mtcars.csv")
  13. #当文件缺少后缀名时，可以指定后缀名打开
  14. a=import("mtcars1", format = "csv")
  16. #Importing Data Lists
  17. b=import_list("list.xlsx")
  19. #export
  20. export(mtcars, "mtcars.csv")

当读取失败(读取样式不是我们需要的），需要指定部分参数,如：

image.pngimage.png

rio包介绍：The idea behind rio is to simplify the process of importing data into R and exporting data from R.rio aims to unify data I/O (importing and exporting) into two simple functions: import() and export() so that beginners (and experienced R users) never have to think twice (or even once) about the best way to read and write R data.The core advantage of rio is that it makes assumptions that the user is probably willing to make.for example, in determining what application is associated with a given file type. By taking away the need to manually match a file type (which a beginner may not recognize) to a particular import or export function, rio allows almost all common data formats to be read with the same function. #**数据输入：**_rio allows you to import files in almost any format using one, typically single-argument, function. import() infers the file format from the file’s extension and calls the appropriate data import function for you, returning a simple data.frame. This works for any for the formats listed above. #缺少后缀名：If for some reason a file does not have an extension, or has a file extension that does not match its actual type, you can manually specify a file format to override the format inference step. #导入列表（excel工作簿）：_Sometimes you may have multiple data files that you want to import. import() only ever returns a single data frame, but import_list() can be used to import a vector of file names into R. This works even if the files are different formats.Similarly, some single-file formats (e.g. Excel Workbooks, Zip directories, HTML files, etc.) can contain multiple data sets.

（3）数据框导出（csv/txt格式）

image.png

（4）R特有数据格式——Rdata

image.png

二、错题重现——时刻关注数据类型

  1. #加载y.Rdata,求gene1列的平均值
  2. load("y.Rdata")
  3. a=mean(y[,1])#看y的类型（矩阵）——里面都是字符型
  4. Warning message:
  5. In mean.default(y[, 1]) : 参数不是数值也不是逻辑值：回覆NA
  6. a=mean(as.numeric(y[,1]))