load(url(....)) vs download.file in R. Why the latter doesn't work when downloading .Rdata files?

Question

I'm reading some of my old R notes and I'm faced with something that make things confusing to me. Here you can find a dummy database with .Rdata extension.

When I use load + url the database is downloaded and read properly:

load(url("http://d396qusza40orc.cloudfront.net/statistics%2Fproject%2Fgss.Rdata"))
str(gss)

But when I try to accomplish same thing using download.file and then readRDS I got an error:

URLtest <- "http://d396qusza40orc.cloudfront.net/statistics%2Fproject%2Fgss.Rdata"
download.file(URLtest,"myfile", method="curl")
readRDS("myfile)
Error in readRDS ("myfile"): unknown input format

The reason I called readRDS can be found here .

So if load is not advised because its side effects (such as silently overwriting files) why does it work in cases like this?

Any reference and comment will be much appreciated.

Answer 1

If the file was created with save() , then you need to use load() to open it. If it was created with saveRDS() , then you can use readRDS() to load it. You cannot open the same file with both load() and readRDS() -- those are two different file formats. It is customary to use an .Rdata extension for files created with save() and .rds for files created with saveRDS() .