A method of easily comparing two currencies.

I'd like to be able to place two currencies on a chart and select a start date to see the percentage difference between them as it changes.

Being able to peg them to a set value of a fiat currency as a percentage I think would help easily know when to trade between them.

For example, select $10,000USD and see what percentage of that ETH is and what BTC is.
This way trading back and forth between non fiat currencies would be clearer without having to do a paper napkin conversion to a fiat to understand if you will make money on them.

Not as much a big deal if the currencies are going up an down together for the most part like BTC/DASH/Doge/LTC, but helpful when one is bucking the trend.

You may be able to do this and as a beginner I don't know how.