The FXB.ta.Performance class calculates performance: the percentage change of each item compared to the initial starting value (not compared to each previous value). It is a value-based calculation, and can be applied to any series of values including the output of another FXB.ta calculation. The calculation has one optional parameter.
| Parameter | Description |
| initial | If not zero (or null), the initial value to compare all the values to. If omitted, the first value in the series is used. |
