test.R

library(dslabs)
library(tidyverse)    # includes readr
library(readxl)

# generate a full path to a file
filename <- "murders.csv"
fullpath <- file.path(path, filename)
fullpath

# copy file from dslabs package to your working directory
file.copy(fullpath, getwd())

# check if the file exists
file.exists(filename)

# inspect the first 3 lines
read_lines("murders.csv", n_max = 3)

# read file in CSV format
dat <- read_csv(filename)

#read using full path
dat <- read_csv(fullpath)
head(dat)

#Ex：
path <- system.file("extdata", package = "dslabs")
files <- list.files(path)
files

filename <- "murders.csv"
filename1 <- "life-expectancy-and-fertility-two-countries-example.csv"
filename2 <- "fertility-two-countries-example.csv"
dat=read.csv(file.path(path, filename))
dat1=read.csv(file.path(path, filename1))
dat2=read.csv(file.path(path, filename2))

# url <- "https://github.com/rafalab/dslabs/master/inst/extdata/murders.csv"
# dat <- read_csv(url)
# download.file(url, "murders.csv")
# tempfile()
# tmp_filename <- tempfile()
# download.file(url, tmp_filename)
# dat <- read_csv(tmp_filename)
# file.remove(tmp_filename)

url <- "https://raw.githubusercontent.com/MyUserName/MyProject/master/MyData.csv "
dat <- read_csv(url)
download.file(url, "MyData.csv")