I'm guessing you are using at TI calculator? I'm not sure what settings you have out of place but you can reset the calculator to it's default settings by doing the following:
1. Take out one battery
2. Hold the clear key
3. Continue to hold the clear key while you replace the battery
4. The calculator will blink on and off.
5. Turn the calculator back on and it should say Ram Cleared.
This should reset your graph settings to their default.