Large amount of text frequency representation visually

I am working on text mining. Now i have some text files which contains millions of words. So i want to determine thier words frequncies. I have two probelms

1. how to process large data in matlab for unique words findings and thier occurance for any text document(contains words in millions)
2. after finding unique words and thier occurance how to represent them in circos/pi etc any graphical representation (as unique words can be in thousands)