#### StdDev

- StdDev(a[ ])
- StdDev(field)
- StdDev(field, groupby)

This function computes the standard deviation of the values referred to by the argument.

Parameters

- a - A Number array.
- field - Values of DBField or formula field.
- groupby - A constant string which indicates the DBField, formula or parameter grouped by.

Return value

Returns a Number value.

Examples

- `Number x = StdDev([1.0, 2.0, 3.0, 4.5, 45.0, 67.0])`
- `Number x[6] = [1.0, 2.0, 3.0, 4.5, 45.0, 67.0];
  Number y = StdDev( x)`
- `Number x = StdDev(@dbfield)`
- `Number x = StdDev(@formula)`
- `Number x = StdDev(@dbfield, @dbfield1)`
- `Number x = StdDev(@dbfield, @formula_groupby)`
- `Number x = StdDev(@dbfield, @parameter)`

Note: If a field is assigned to a variable, for example x, the variable x will lose the characteristic of representing a group of values. The following formula will then be treated as incorrect.

`Number x = @dbfield;
Number y = StdDev( x); // system will prompt you that there is no such kind of function.`