====== Creating models ======

Ecolego was originally designed for solving systems of ordinary differential equations, but you can also create models containing only algebraich expressions.

{{creating_models.png?500|model}}

Models are defined by creating different [[block|bloks]]. 

Models may be developed by using [[graph_window|Graph window]] or [[matrix_window|Matrix window]]. 

Most common blocks are:

* **[[Expression|Expression]]**  -  Allows you to write an equation, in which you refer to other building blocks.

* **[[Parameter|Parameter]]**  - Lets the user enter a value which will remain constant during the simulation, and which can be assigned a probability distribution.

* **[[time_series_page|Time series]]** - Is used to include time based measurements in a model, for instance precipitation rates, the past behavior of a stock or the weight of a persons life time.

* **[[compartment|Compartment]]**- Represents a physical or imaginary quantity.Compartments are connected with [[Transfer|transfer]]** blocks. 

The typical type of model implemented in Ecolego is called a compartment model. The compartment model describes flow of species between compartments. Species is the scientific term for whatever it is we are modelling the dynamics of – materials, chemicals, money, people, goods. Fluxes between compartments are described by equations. The fluxes can be linear (proportional), non-linear or even instant.

Ecolego allows the user to define things in the order he feels like bu using [[block|bloks]]. A list of errors in equations is presented that needs to be dealt with before a simulation can be run. 
Ecolego will help the user with unit checking, but again, this is something the user can choose to deal with when he feels it is necessary.

===== See also =====

  * [[Blocks_window|Blocks window]]
  * [[Matrix_window|Matrix window]]
  * [[Graph_window|Graph window]]