Correlation Trading is a financial app for the back-test of trading systems based on the main US, Europe and Asian market indices. You can choose to trade any of the supported indices (the "trading instrument") for a simulated trading period ranging from the past year to the past month. The signal generator (long/short positions) is provided by the sign of a selected price parameter of any of the indices, which is sampled a given number of days before the trading day, i.e. the Open-Close Range (OCR) sign of the traded index sampled at the n-th day before the trading day. A stop loss and a take profit level can also be specified. It is assumed that all positions are entered when the market opens (at the opening price), and closed when one of the following events (in order of priority) occurs: 1) the market reaches the stop loss price; 2) the market reaches the take profit price; 3) the market closes.