When the price trend has moved from one trend to another, it shifts to the right, signaling a trend change. The reversal criteria set how much the price has to move away from the high or low in the price trend to create a new trend or, in other words, how much the price has to move in order for a column of Xs to become a column of Os (or vice versa). This is usually set at three but it can also be set according to the technician's discretion. The other critical point of a P&F chart is the reversal criteria. On most charts where the price is between $20 and $100, a box represents $1, or 1 point for the stock. Each box on the chart represents the price scale, which adjusts depending on the price of the stock the higher the stock's price, the more each box represents. The Xs represent upward price trends and the Os represent downward price trends. The key unit in a P&F chart is the point, or unit of price.
Both axis of P&F charts' are dependent on price, rather than one being based on price and the other on date.