Determining profitability

[NOTAL]

I'm thinking of building a mining machine, and am trying to figure out if it will be profitable. I've used this: http://lorelei.kaverit.org/cgi/calc.py to calculate the profitability based on today's difficulty and compared with today's BTC/USD rate. But I would really like to see how the [BTC/USD rate]/[difficulty] has changed over time so I can try to guess at future profitability. I can find graphs for each (difficulty here: http://bitcoin.sipa.be/ and BTC/USD charts from MtGox), but not the raw numbers. I need to find the raw numbers so I can compare them and make a value/difficulty graph.

Does anyone know where I can get the raw data for difficulty and exchange rate? (or better yet, a graph of the ratio that someone has already put together)

Thanks

[Grinder]

Raulo has done the job for you here: http://bitcoin.atspace.com/income.html

If it doesn't load you'll have to try later.

[proudhon]

Even without the data you can always calculate what would need to be the case to remain profitable, or to remain as profitable as you were at a given difficulty level.  For example, if Bitcoin Charts is right about the next difficulty level, then the exchange rate needs to be at least $1.77 for me to be as profitable as I was at the last difficulty at the current exchange rate, and so on.