A **Function** can be calculated as it was called on any previous bar.
Every **Function** has optional **BarsBack** parameter
that specifies on which bar the function is calculated. If **BarsBack**
parameter isn't specified or is equal to 0, then function is calculated on current
bar. If **BarsBack** parameter is set to 1 function is calculated on
prvious bar and so on. **BarsBack** parameter is market with blue text
color in the Code Editor.

**
Example:**

```
a = Summation(Bars.Close, 10); // Calculating on current bar
a = Summation(Bars.Close, 10,
```**1**); // Calculating on previous bar
a = Summation(Bars.Close, 10, **2**); // Calculation on third bar back
a = Summation(Bars.Close, 10, **10**); // Calculation on the tenths bar back

See also Functions.