Datastream functions (there are now more than 75 functions) are statistical and display operators that allow you to calculate and view data in the way you want. For example, you may need to look at a moving average or percentage change rather than an actual price movement. You can combine several functions (with maths operators and constants) to form expressions and save these using the Expression builder. This is useful where the same expression is used frequently.
For each function definition, the function format is given, plus examples of the function usage.