tidyverse套件集裡的readr套件，目的在處理資料來源的匯入，當然如有其他xml等資料要處理，就需要搭配xml2或是XML套件。

#準備工作
#install.packages("tidyverse")
library(readr)

存檔

先來看看將資料寫成檔案存放部分

#先做個dftemp的當作例子
dftemp <- data.frame(
  name = c("Sam", "Kimi", "Albert"),
  scoreA = c(67, 80, 64),
  scoreB = c(56, 90, 50),
  group = letters[1:3]
)
#Save2File
#Comma delimited 
##filewrite_csv(x, path, na = "NA", append = FALSE,col_names = !append)
    write_csv(dftemp,path="D:/Users/Desktop/write2csv.csv")
#File with arbitrary delimiter
##write_delim(x, path, delim = " ", na = "NA",append = FALSE, col_names = !append)
    write_delim(dftemp,path="D:/Users/Desktop/writedelim.csv",delim = "~")
#CSV for excel
##write_excel_csv(x, path, na = "NA", append =FALSE, col_names = !append)
    write_excel_csv(dftemp,path="D:/Users/Desktop/write2excelcsv.csv")

write_csv跟write_excel_csv並無差別。

讀檔

先來看看有表格樣式的原始資料處理(Tabular Data)，這部分的概念，如各位日常使用Excel 作業處理資料匯入時的概念與處理，幾乎是完全一致的。

#Read Tabular Data
##讀入逗號分隔號分隔的檔案Comma Delimited Files
write_file(x = "a,b,c\n1,2,3\n4,5,NA", path = "file.csv")
read_csv("file.csv")

##讀入分號分隔號分隔的檔案Semi-colon Delimited Files
write_file(x = "a;b;c\n1;2;3\n4;5;NA", path = "file2.csv")
read_csv2("file2.csv")

##讀入使用分隔號分隔的檔案Files with Any Delimiter
write_file(x = "a|b|c\n1|2|3\n4|5|NA", path = "file.txt")
read_delim("file.txt", delim = "|")

##讀入使用固定欄位寬度分隔的檔案Fixed Width Files
write_file(x = "a b c\n1 2 3\n4 5 NA", path = "file.fwf")
read_fwf("file.fwf", col_positions = c(1, 3, 5))

##讀入使用Tab分隔的檔案Tab Delimited Files
write_file(x = "a\tb\tc\n1\t2\t3\n4\t5\tNA", path = "file.tsv")
read_tsv("file.tsv") 

讀檔時重要的參數補充!

#USEFUL ARGUMENTS
#範例:Example file
write_file("a,b,c\n1,2,3\n4,5,NA","file.csv")
f <- "file.csv"

#宣告此資料來源，無欄位，第一欄就是資料，非欄名。No header
    read_csv(f, col_names = FALSE)
#給定欄位名稱 Provide header
    read_csv(f, col_names = c("x", "y", "z"))
#給定跳過處理哪一行 Skip lines
    read_csv(f, skip = 1)
#給定處理資料筆數 Read in a subset
    read_csv(f, n_max = 1) #Maximum number of records to read.
#直接給定Missing Values
    read_csv(f, na = c("1","3"))

#比較一下
write_csv(dftemp, path = "D:/Users/Desktop/fileX.csv")
x<-read_csv("D:/Users/Desktop/fileX.csv")
y<-read.csv("D:/Users/Desktop/fileX.csv")

發現到使用read_csv需要給定欄位type。(想偷懶的話就用read.csv)

x<-read_csv("D:/Users/Desktop/fileX.csv");problems()#problems()展開問題對話
#根據建議，把資料補上
x<-read_csv("D:/Users/Desktop/fileX.csv", col_types = cols(
  name = col_character(),
  scoreA = col_integer(),
  scoreB = col_integer(),
  group = col_character()
))
#看看結果囉
View(x)

參考資料

R-cheatsheets-readr