R語言中文件的讀寫

1. JSON文件：

library(jsonlite)

file <- "/Users/abcd/Documents/diff_files/json/test.json"

json1 <- read_json(path = file)

write_json(json1, path = file)

2. YAML文件：

library(yaml)

file <- "/Users/abcd/Documents/diff_files/yaml/test.yaml"
write_yaml(data.frame(a = 1:10, b = letters[1:10], c= 11:20),  path = file)

read_yaml(file = file)

3. CSV文件：

path1 <- "/Users/abcd/Documents/diff_files/csv/test5.txt"
write.table(file = path1, 
            x = data.frame(id = 1:(26e4), name = rep(letters, times = 1e4)),
            row.name = FALSE, col.names = TRUE, append = FALSE, sep = "\t")

subset1 <- read.table(file = path1, sep = "\t", header = TRUE)
# 讀取全部數據
subset2 <- read.table(file = path1, sep = "\t",
                      skip = 15, header = FALSE)
# 從第16行開始讀取
subset3 <- read.table(file = path1, sep = "\t",
                      skip = 15, nrow = 26, header = FALSE)
# 從第16行開始讀取，讀取26行
subset4 <- read.table(file = path1, sep = "\t", 
                      skip = 16, nrows = 26, 
                      colClasses = c("integer", "character"))
# 從第16行開始讀取，讀取26行，指定每列的類型，提高讀取速度

4. 使用readLines控制讀取行數：

path1 <- "/Users/abcd/Documents/diff_files/csv/test5.txt"
con1 <- file(description = path1, open = "r")
data1 <- readLines(con = con1, n = 1e5)
close(con1)
length(data1)