## diff (var x, int Period): var

Returns the difference of **x** to its value from **Period** bars before.
### Parameters:

**x** |
Variable for difference calculation. |

### Returns

**x - previous x**

### Remarks

- This function generates a series and thus must be called in a fixed order in the script.
**diff(log(x),1)** returns the log return of **x** , since **log(a/b) = log(a) - log(b)**.

### Example:

*// generate a price difference serie*
vars Changes = series(diff(priceClose(),1));

### See also:

series, rev, ROCP
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