# Choice Modeling - Diagnostic - Trace Plots extension

Create a diagnostic plot of the trace of the parameter estimates

Takes a hierarchical Bayes (Stan) output and produces trace plots of the mean and standard deviation parameters for the distribution from which individual coefficients are sampled. For more information on how to interpret this output, see this blog post, which was written for the closely-related MaxDiff analysis.

Note that numeric variables are shown as scaled (this is done to improve model sampling). The prefix "Scaled" is added to numeric variable names. To descale the numeric variable coefficients, multiply them by the multipliers that can be obtained by creating a new R output and typing in choice.model\$numeric.scaling into the R CODE editor (choice.model needs to be replaced with the name of the choice model output) and clicking calculate. The output will contain a list of multipliers to be used for each numeric variable.

## Technical details

Whenever Hierarchical Bayes analysis is run with multiple classes, an attempt will be made to match class labels between chains (note that it is often not possible to match class labels). If this succeeds, or if only one chain was specified, one set of mean and standard deviation parameters will be shown for each class. If this attempt is unsuccessful, the trace plots will not be able to be displayed.

## How to apply this QScript

• Start typing the name of the QScript into the Search features and data box in the top right of the Q window.
• Click on the QScript when it appears in the QScripts and Rules section of the search results.

OR

• Select Automate > Browse Online Library.
• Select this QScript from the list.

## Customizing the QScript

This QScript is written in JavaScript and can be customized by copying and modifying the JavaScript.

• Start typing the name of the QScript into the Search features and data box in the top right of the Q window.
• Hover your mouse over the QScript when it appears in the QScripts and Rules section of the search results.
• Press Edit a Copy (bottom-left corner of the preview).
• Modify the JavaScript (see QScripts for more detail on this).
• Either:
• Run the QScript, by pressing the blue triangle button.
• Save the QScript and run it at a later time, using Automate > Run QScript (Macro) from File.

### Customizing QScripts in older versions

• Create a new text file, giving it a file extension of .QScript. See here for more information about how to do this.
• Modify the JavaScript (see QScripts for more detail on this).
• Run the file using Automate > Run QScript (Macro) from File.

## JavaScript

includeWeb("QScript R Output Functions");

const menu_location = "Choice Modeling > Diagnostic > Trace Plots";
var selected_items = project.report.selectedRaw();
var selected_item = selected_items[0];
var selected_group = selected_item.type == "ReportGroup" ? selected_item : selected_item.group;
var plot = selected_group.appendStandardR("Choice Modeling - Trace Plots", { "formInput": selected_item.guid});
selected_group.moveAfter(plot, selected_item);
project.report.setSelectedRaw([plot]);


## Acknowledgements

Uses the rstan R package.

## References

McLean, M. W. (2018, July 24). How to Use Hierarchical Bayes for Choice Modeling in Displayr [Blog post]. Accessed from https://www.displayr.com/how-to-hierarchical-bayes-choice-model-displayr/.

Yap, J. (2018, January 16). Checking Convergence When Using Hierarchical Bayes for MaxDiff [Blog post]. Accessed from https://www.displayr.com/convergence-hb-maxdiff/.