I am interested in analyzing balance sheets and income statements using R. I have seen that there are R packages that pull information from Yahoo and Google Finance, but all the examples I have seen concern historical stock price information. Is there a way I can pull historical information from balance sheets and income statements using R?
You are making the common mistake of confusing 'access to Yahoo or Google data' with 'everything I see on Yahoo or Google Finance can be downloaded'.
When R functions download historical stock price data, they almost always access an interface explicitly designed for this purpose as e.g. a cgi handler providing csv files given a stock symbol and start and end date. So this easy as all we need to do is form the appropriate query, hit the webserver, fetch the csv file an dparse it.
Now balance sheet information is (as far as I know) not available in such an interface. So you will need to 'screen scrape' and parse the html directly.
It is not clear that R is the best tool for this. I am aware of some Perl modules for the purpose of getting non-time-series data off Yahoo Finance but have not used them.