Are there any limits on downloading data using the R library?

See below for Quandl’s rate limits:

Anonymous users have a limit of 20 calls per 10 minutes and 50 calls per day.

Authenticated users have a limit of 300 calls per 10 seconds, 2,000 calls per 10 minutes and a limit of 50,000 calls per day. 

Authenticated users of free data feed have a concurrency limit of one; that is, they can make one call at a time and have an additional call in the queue.

Premium data subscribers have a limit of 5,000 calls per 10 minutes and a limit of 720,000 calls per day.