# Distributions

Many ST-Sim parameters, such as Transition Multipliers, can be sampled from probability **Distributions**. SyncroSim comes with a set of predefined distributions such as *Uniform*, *Normal Beta* and *Gamma*. However, there may be instances where end users require other distributions. The Project scope Distributions datasheet can be used to specify the name and description for discrete user defined distributions. The values for these distributions can then be defined in the scenario scope, Distributions datasheet.

## Built-in Distributions

Distribution Type | Description |
---|---|

Beta | Continuous probability distribution, used to model variables with a limited range (such as 0 to 1). |

Normal | Continuous probability distribution with a symmetrical probability density. |

Uniform | Symmetric continuous probability distribution, where every value between the min and max has an equal probability for being selected. |

Uniform Integer | Discrete uniform probability distribution that returns only integers. Every integer value between the min and max has an equal probability for being selected. |

## Built-in Sampling Frequencies

When using a probability distribution, users can also specify the frequency at which the distribution will be sampled. The available frequencies are:

Frequency | Description |
---|---|

Iteration | Samples at the beginning of every iteration. |

Timestep | Samples at the beginning of every timestep. |

Iteration and Timestep | Samples at the beginning of every iteration and every timestep. |

## Custom Distributions

Users may optionally create custom probability distributions. The following fields are required when constructing custom probability distributions:

### Name

The name of the distribution.

### Description (optional)

Users may optionally enter a description of the distribution.