Important: Read this before posting to this forum

  1. This forum is for questions related to the use of Apollo. We will answer some general choice modelling questions too, where appropriate, and time permitting. We cannot answer questions about how to estimate choice models with other software packages.
  2. There is a very detailed manual for Apollo available at http://www.ApolloChoiceModelling.com/manual.html. This contains detailed descriptions of the various Apollo functions, and numerous examples are available at http://www.ApolloChoiceModelling.com/examples.html. In addition, help files are available for all functions, using e.g. ?apollo_mnl
  3. Before asking a question on the forum, users are kindly requested to follow these steps:
    1. Check that the same issue has not already been addressed in the forum - there is a search tool.
    2. Ensure that the correct syntax has been used. For any function, detailed instructions are available directly in Apollo, e.g. by using ?apollo_mnl for apollo_mnl
    3. Check the frequently asked questions section on the Apollo website, which discusses some common issues/failures. Please see http://www.apollochoicemodelling.com/faq.html
    4. Make sure that R is using the latest official release of Apollo.
  4. If the above steps do not resolve the issue, then users should follow these steps when posting a question:
    1. provide full details on the issue, including the entire code and output, including any error messages
    2. posts will not immediately appear on the forum, but will be checked by a moderator first. This may take a day or two at busy times. There is no need to submit the post multiple times.

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by stephanehess
23 Jul 2020, 15:48
Forum: Model specification
Topic: ICLV
Replies: 3
Views: 5282

Re: ICLV

Hi

when the outcome is just a yes/no answer, and the attributes are situation rather than alternative specific, then you just make the utility 0 for one of the two alternatives, and put the attributes in the other utility. Only differences in utility matter

Hope that helps

Stephane
by stephanehess
23 Jul 2020, 15:27
Forum: Model specification
Topic: Simultaneous estimation of parameters with potentially different scale
Replies: 10
Views: 17150

Re: Simultaneous estimation of parameters with potentially different scale

Hi

in order to estimate scale differences, at least one of the parameters needs to be shared between the samples. That's not the case in your specification, so your model is overspecified

NB. You're also missing the ASC for the second group, but maybe this was intentional

Best wishes

Stephane
by stephanehess
23 Jul 2020, 15:24
Forum: Model specification
Topic: ICLV
Replies: 3
Views: 5282

Re: ICLV

Hi

it's difficult to offer general help without specific questions or issues. Did you look at the ICLV examples on the website?

Best wishes

Stephane
by stephanehess
20 Jul 2020, 14:36
Forum: Bug reports
Topic: Problems with multi-core in R4.x
Replies: 1
Views: 5978

Re: Problems with multi-core in R4.x

Hi Yishih Thanks for bringing this issue to our attention. This is indeed a wider RStudio issue rather than an Apollo issue. We have implemented a fix in v0.1.1 that creates the cores sequentially on MacOS systems. It adds a small additional setup time in creating the cores but has no impact on run ...
by stephanehess
18 Jul 2020, 22:06
Forum: Errors during model validation and/or estimation.
Topic: An error when estimating nonlinear utility specification
Replies: 3
Views: 5541

Re: An error when estimating nonlinear utility specification

Tim

good lesson to always track back to see where you get the first error

Best wishes

Stephane
by stephanehess
18 Jul 2020, 16:04
Forum: Errors during model validation and/or estimation.
Topic: An error when estimating nonlinear utility specification
Replies: 3
Views: 5541

Re: An error when estimating nonlinear utility specification

Tim

do you get any errors when running apollo_inputs = apollo_validateInputs()

Stephane
by stephanehess
17 Jul 2020, 11:07
Forum: Other
Topic: Online course in choice modelling and stated choice survey design?
Replies: 1
Views: 9791

Re: Online course in choice modelling and stated choice survey design?

This year, the courses organised by the Choice Modelling Centre will be available online too (http://cmc.leeds.ac.uk/courses-phds/cpd/)

To discuss one-to-one Apollo training, please write to contact@apollochoicemodelling.com
by stephanehess
13 Jul 2020, 20:30
Forum: Bug reports
Topic: Prediction of mixed MDCEV models
Replies: 2
Views: 6878

Re: Prediction of mixed MDCEV models

Hi Yishih On point 1, this was a bug. This has been fixed in v0.1.1 which you can download from http://www.apollochoicemodelling.com/code.html already and which will be released on CRAN sometime this summer On point 2, sorry, but these means and standard deviations are computed inside the code in an...
by stephanehess
10 Jul 2020, 15:58
Forum: Estimation results
Topic: Could the LL of a full model worse than that for the reduced model?
Replies: 12
Views: 18555

Re: Could the LL of a full model worse than that for the reduced model?

Tim the sign of the correlation depends on the sign of the product of hinc_sig_20* hinc_sig_20_90. Section Section 9.2.5 in Kenneth Train's book. The Delta method can be used for this, but you'd need to work out the derivatives yourself - they're not implemented in Apollo for the standard errors. Be...
by stephanehess
09 Jul 2020, 22:03
Forum: Estimation results
Topic: Could the LL of a full model worse than that for the reduced model?
Replies: 12
Views: 18555

Re: Could the LL of a full model worse than that for the reduced model?

Hi Tim I've looked into your model in detail and I believe I have found the reason this is happening. In your base specification, you use the same coefficient whether the treatment is 20 or 90. In your more general model, you use separate parameters. Now, you see that in the MNL model, the more gene...

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