The `download.file()` function in R is used to download a single file from the internet and store it in a specified location. The function takes two arguments:
- `url`: The URL of the file to be downloaded.
- `destfile`: The destination file path where the file will be saved.
The `download.file()` function also has a number of other optional arguments, including:
* `method`: The method to be used for downloading the file. The default method is `"internal"`, but other methods include `"wininet"` (Windows only), `"libcurl"`, `"wget"`, and `"curl"`.
- `quiet`: A logical value indicating whether or not to print progress messages.
- `mode`: The mode in which the file should be opened. The default mode is `"w"`, which creates a new file if it does not exist or overwrites an existing file.
- cacheOK`: A logical value indicating whether or not to cache the file. If `cacheOK` is `TRUE`, the file will be downloaded only if it does not already exist in the cache.
The `download.file()` function returns a logical value indicating whether or not the download was successful.
Here is an example of how to use the `download.file()` function to download a CSV file from the internet:
url <- "https://raw.githubusercontent.com/hadley/tidyverse/master/data/iris.csv"
destfile <- "iris.csv"
download.file(url, destfile)
This code will download the `iris.csv` file from the GitHub repository and save it to the current working directory.
The `download.file()` function is a useful tool for getting data from the internet. It can be used to download a variety of file formats, including CSV, tab-delimited, and Excel files. The function is also reproducible, so you can be sure that you will always be downloading the same file.
- The download.file() function can be used to download a single file from the internet. The file must be accessible via a URL that starts with either http:// or https://.
- If the URL starts with https://, you may need to set the method argument to "curl" on a Mac. This is because the default download method for Mac, "internal", does not support HTTPS downloads.
- If the file is large, the download process may take a while. You can use the quiet argument to suppress progress messages if you don't want to be notified of the download progress.
- It is a good idea to record the date and time when you downloaded the file. This can be useful if you need to track the provenance of the data.
url <- "https://www.r-project.org/stats/datasets/cars.csv"
destfile <- "cars.csv"
download.file(url, destfile)
How to download a file from the web?
fileUrl <- "https://xyz.example.com"
download.file(fileUrl, destfile="./xyz/ships.csv", method="curl")
list.files("./xyz")
This code will download a file from the web using the `download.file()` function in R. The code first defines a variable called `fileUrl` that contains the URL of the file to be downloaded. Then, the `download.file()` function is used to download the file to the specified location. The `destfile` argument specifies the location where the file should be saved. In this case, the file will be saved to the `./xyz` directory with the filename `ships.csv`. The `method` argument specifies the method to be used for downloading the file. In this case, the `curl` method is used.
The last line of code, `list.files("./xyz")`, lists the files in the `./xyz` directory. This can be used to verify that the file has been downloaded successfully.
- `fileUrl` is a character string that contains the URL of the file to be downloaded.
- `download.file()` is a function that downloads a file from the web. The `destfile` argument specifies the location where the file should be saved. The `method` argument specifies the method to be used for downloading the file.
- `list.files()` is a function that lists the files in a directory.
