Specify Parameters

In the Specify Parameters dialog box you can manually specify the parameter values for the distribution of the selected field. You can also choose a different distribution for the selected field.

The Specify Parameters dialog box can be opened in three ways:

  • Double click on a field name in the Simulated Fields table in the Simulation Generate node dialog box.
  • Click the Parameters or Min, Max column of the Simulated Fields table, and choose Specify from the list.
  • In the Simulated Fields table, select a row, and then click the Edit distribution parameters icon.

Field. Contains the name of the selected field. This text cannot be edited.

Distribution. Contains the distribution of the selected field. This is taken from the Simulated Fields table. The distribution can be changed by clicking the arrow and selecting a distribution from the drop-down list. The available distributions depend on the storage type of the selected field.

Sides. This option is only available for the when the dice distribution is selected in the Distribution field. Click the arrows to select the number of sides, or categories, to split the field in to. The minimum number of sides is two, and the maximum is 20. The number of sides is initially set to 6.

Distribution parameters. The Distribution parameters table contains one row for each parameter of the chosen distribution.
Note: Distribution uses a rate parameter, with a shape parameter α = k and an inverse scale parameter β = 1/θ.
The table contains two columns:
  • Parameter. Contains the names of the parameters. This column cannot be edited.
  • Value(s). Contains the values of the parameters. If the Simulation Generate node has been created or updated from a Simulation Fitting node, the cells in this column contain the parameter values that have been determined by fitting the distribution to the historical data. If the Simulation Generate node has been added to the stream canvas from the Source nodes palette, the cells in this column are empty. The values can be edited by typing in the cells. See the topic Distributions for more information about the parameters needed by each distribution, and acceptable parameter values.

    Multiple values for a parameter must be separated by commas. Specifying multiple values for a parameter will define multiple iterations of the simulation. You can only specify multiple values for one parameter.

    Note: For fields with datetime storage types, you must specify the distribution parameters as integers. For example, to specify a mean date of 1 January 1970, use the integer 0.
Note: When the dice distribution is selected, the Distribution parameters table is slightly different. The table contains one row for each side (or category). The table contains a Value column and a Probability column. The Value column contains a label for each category. The default values for the labels are the integers 1-N, where N is the number of sides. The labels can be edited by typing in the cells. Any value can be entered into the cells. If you want to use a value that is not a number, the storage type of the data field must be changed to string if the storage type is not already set to string. The Probability column contains the probability of each category. The probabilities cannot be edited, and are calculated as 1/N.

Preview. Shows a sample plot of the distribution, based on the specified parameters. If two or more values have been specified for one parameter, sample plots for each value of the parameter are shown. If historical data is available for the selected field, the plot of the distribution is superimposed on a histogram of the historical data.

Optional Settings. Use these options to specify a minimum value, a maximum value, or both for the simulated data. Simulated data that are smaller than the minimum value and larger than the maximum value will be rejected, even though they would be valid for the specified distribution.

  • Specify minimum. Select to enable the Reject values below field. The check box is disabled if the Empirical distribution is selected.
  • Reject values below. Only enabled if Specify minimum is selected. Enter a minimum value for the simulated data. Any simulated values smaller than this value will be rejected.
  • Specify maximum. Select to enable the Reject values above field. The check box is disabled if the Empirical distribution is selected.
  • Reject values above. Only enabled if Specify maximum is selected. Enter a maximum value for the simulated data. Any simulated values larger than this value will be rejected.

OK. Closes the dialog box and updates the values of the Distribution, Parameters and Min, Max columns of the Simulated Fields table for the selected field. The icon in the Status column is also updated to reflect the selected distribution.

Cancel. Closes the dialog box. Any changes that have been made are discarded.