simgennode properties

Last updated: Jan 18, 2024

Sim Gen node icon The Simulation Generate (Sim Gen) node provides an easy way to generate simulated data—either from scratch using user specified statistical distributions or automatically using the distributions obtained from running a Simulation Fitting (Sim Fit) node on existing historical data. This is useful when you want to evaluate the outcome of a predictive model in the presence of uncertainty in the model inputs.

Table 1. simgennode properties
`simgennode` properties	Data type	Property description
`fields`	Structured property	See example
`correlations`	Structured property	See example
`keep_min_max_setting`	boolean
`refit_correlations`	boolean
`max_cases`	integer	Minimum value is 1000, maximum value is 2,147,483,647
`create_iteration_field`	boolean
`iteration_field_name`	string
`replicate_results`	boolean
`random_seed`	integer
`parameter_xml`	string	Returns the parameter Xml as a string

fields example

This is a structured slot parameter with the following syntax:

simgennode.setPropertyValue("fields", [
    [field1, storage, locked, [distribution1], min, max],
    [field2, storage, locked, [distribution2], min, max],
    [field3, storage, locked, [distribution3], min, max]
])

distribution is a declaration of the distribution name followed by a list containing pairs of attribute names and values. Each distribution is defined in the following way:

[distributionname, [[par1], [par2], [par3]]]

simgennode = modeler.script.stream().createAt("simgen", u"Sim Gen", 726, 322)
simgennode.setPropertyValue("fields", [["Age", "integer", False, ["Uniform",[["min","1"],["max","2"]]], "", ""]])

For example, to create a node that generates a single field with a Binomial distribution, you might use the following script:

simgen_node1 = modeler.script.stream().createAt("simgen", u"Sim Gen", 200, 200)
simgen_node1.setPropertyValue("fields", [["Education", "Real", False, ["Binomial", [["n", 32],
 ["prob", 0.7]]], "", ""]])

The Binomial distribution takes 2 parameters: n and prob. Since Binomial does not support minimum and maximum values, these are supplied as an empty string.

Note: You can't set the distribution directly; you use it in conjunction with the fields property.

The following examples show all the possible distribution types. Note that the threshold is entered as thresh in both NegativeBinomialFailures and NegativeBinomialTrial.

stream = modeler.script.stream()

simgennode = stream.createAt("simgen", u"Sim Gen", 200, 200)

beta_dist = ["Field1", "Real", False, ["Beta",[["shape1","1"],["shape2","2"]]], "", ""]
binomial_dist = ["Field2", "Real", False, ["Binomial",[["n" ,"1"],["prob","1"]]], "", ""]
categorical_dist = ["Field3", "String", False, ["Categorical", [["A",0.3],["B",0.5],["C",0.2]]], "", ""]
dice_dist = ["Field4", "Real", False, ["Dice", [["1" ,"0.5"],["2","0.5"]]], "", ""]
exponential_dist = ["Field5", "Real", False, ["Exponential", [["scale","1"]]], "", ""]
fixed_dist = ["Field6", "Real", False, ["Fixed", [["value","1" ]]], "", ""]
gamma_dist = ["Field7", "Real", False, ["Gamma", [["scale","1"],["shape"," 1"]]], "", ""]
lognormal_dist = ["Field8", "Real", False, ["Lognormal", [["a","1"],["b","1" ]]], "", ""]
negbinomialfailures_dist = ["Field9", "Real", False, ["NegativeBinomialFailures",[["prob","0.5"],["thresh","1"]]], "", ""]
negbinomialtrial_dist = ["Field10", "Real", False, ["NegativeBinomialTrials",[["prob","0.2"],["thresh","1"]]], "", ""]
normal_dist = ["Field11", "Real", False, ["Normal", [["mean","1"] ,["stddev","2"]]], "", ""]
poisson_dist = ["Field12", "Real", False, ["Poisson", [["mean","1"]]], "", ""]
range_dist = ["Field13", "Real", False, ["Range", [["BEGIN","[1,3]"] ,["END","[2,4]"],["PROB","[[0.5],[0.5]]"]]], "", ""]
triangular_dist = ["Field14", "Real", False, ["Triangular", [["min","0"],["max","1"],["mode","1"]]], "", ""]
uniform_dist = ["Field15", "Real", False, ["Uniform", [["min","1"],["max","2"]]], "", ""]
weibull_dist = ["Field16", "Real", False, ["Weibull", [["a","0"],["b","1 "],["c","1"]]], "", ""]

simgennode.setPropertyValue("fields", [\
beta_dist, \
binomial_dist, \
categorical_dist, \
dice_dist, \
exponential_dist, \
fixed_dist, \
gamma_dist, \
lognormal_dist, \
negbinomialfailures_dist, \
negbinomialtrial_dist, \
normal_dist, \
poisson_dist, \
range_dist, \
triangular_dist, \
uniform_dist, \
weibull_dist
])

correlations example

This is a structured slot parameter with the following syntax:

simgennode.setPropertyValue("correlations", [
    [field1, field2, correlation],
    [field1, field3, correlation],
    [field2, field3, correlation]
])

Correlation can be any number between +1 and -1. You can specify as many or as few correlations as you like. Any unspecified correlations are set to zero. If any fields are unknown, the correlation value should be set on the correlation matrix (or table). When there are unknown fields, it's not possible to run the node.