====== Varying parameters in a simulation ======
 
Nothing should remain constant in a dynamic model. In this respect, Dinamica EGO enables to vary model parameters either in different simulation phases or at each time step.  In the Stack tab, a set of Select Functors can be used to change the values of input parameters according to the model step.

**Using different transition matrices** 

For examples, instead of using only a constant transition matrix, //[[:Select Transition Matrix]]// enables the use of different transition matrices in a simulation.

To start, load the model ''simulate_deforestation_using_multiple_transition_matrix.egoml'' from ''\Guidebook_Dinamica_5\Models\additional_resources_lucc\multiple_parameters\simulate_deforestation_using_multiple_transition_matrix''

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Using more than one transition matrix in a model is quite simple. In this version of a deforestation model, //[[:Select Transition Matrix]]// was added to allow the choice of a transition matrix according to the model step. Each transition matrix is entered in a //[[:Number Transition Matrix]]//, click on this functor with the Edit Functor. 

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**Matrix Number** in this functor indentifies the model step in which this transition matrix begins to operate. The model will use this matrix until it finds a //[[:Number Transition Matrix]]// with **Matrix Number** that corresponds to the current model step, while from this point onwards //[[:Select Transition Matrix]]// switches to the new transition matrix. 
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<WRAP column 30%>
<note tip>**TIP**: you can use as many transition matrices as time steps.  You just need to add more //[[:Number Transition Matrix]]// functors and number them according to the model time intervals.</note>
</WRAP>
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**Using different Weights of Evidence coefficients** 

The same procedure applies to the selection of other model parameters, such as the Weight of Evidence 
coefficients. 
Load the model: ''simulate_deforestation_using_multiple_transition_matrix_and_weights.egoml'' from ''\Guidebook_Dinamica_5\Models\additional_resources_lucc\multiple_parameters\simulate_deforestation_using_multiple_transition_matrix_and_weights''

A //[[:Select Weights]]// functor is added to the model to enable the selection of more than one Weights of Evidence coefficient files. A //[[:Number Weight]]// is inserted within the container //[[:Select Weights]]// for each Weights of Evidence coefficient file. Another //[[:Load Weights]]// is added to the model in the outside part of the main loop (//[[:Repeat]]//). This functor loads the coefficients from a file and is connected to one of the //[[:Number Weights]]// inside the //[[:Select Weights]]//. Open each one of the //[[:Number Weights]]// and edit the **Weight Number** field to define the step when each coefficient file begins to take part in the model.

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[[tutorial:using_subregions_in_a_simulation_model|Next Lesson]]