Returns the gamma distribution.
| Name | Type | Description |
| arg1 | number | The value at which the distribution will be calculated, a nonnegative number. |
| arg2 | number | The alpha parameter of the distribution, a positive number. |
| arg3 | number | The beta parameter of the distribution, a positive number. If this parameter is equal to 1, the function returns the standard gamma distribution. |
| arg4 | boolean | A logical value (true> or false) that determines the function form. If it is true, the function returns the cumulative distribution function. If it is false, the function returns the probability density function. |