ApolloChoiceModelling forum

Hi Peter,

Yes, adding more RAM to your computer should help. But it is quite hard to predict how much it will be used (as I mentioned, R's memory usage is a bit obscure). If you want to add more RAM, I would go to the max you can afford or your computer can take.

Another practical solution is ...

Hi,

I am not aware of techniques for efficient experimental design for discrete choice latent class models. That said, Ngene is the leading software for generating discrete choice experimental designs, so you may want to look into it. A quick glance through their manual did not return a match for ...

Hi Dominik,

While I am no expert in Best-Worst, my limited experience with it is that a wrong scale parameter simply indicates that the model formulation is not supported by the data. This would be similar to obtaining an out-of-range nest parameter in a nested logit, which simply means that the ...

Sure you can. You can look at example Hybrid_with_continuous_measurement in the webpage for a template on how to implement it. You may also want to look at Ben-Akiva et al (2002) for the theory behind it.

Hi Peter,

The R language can be quite memory hungry. In the particular case of Apollo, this usually manifest in hybrid models, where the multiple components (measuring + choice) end up consuming significant amounts of memory.

Here are a few tips to reduce memory consumption (at the cost of slower ...

Hi Ming,

I can’t recall any particular set of good practices when including systematic taste variations in WTP-space models. After a quick google search, most papers I found deal with parametrising random coefficient in WTP-space, without going into details of systematic taste variation or ...

Hi,

I am not sure I got all the details right of what you want to do, but let’s start with the following case and take it from there.

Let’s say your choice model has 5 alternatives: working 1, 2, 3, 4, or 5 days a week. And you only have two explanatory variables: income_j (the income that the ...

Hi Johnathan,

As Stephane mentioned, we thought about making apollo_searchStart, apollo_bootstrap, and apollo_outOfSample perform parallel estimation at the model level before, as opposed to using parallel estimation within each model. However, we did not do it because sharing the pre-processing ...

Hi Gaby,

The code looks good to me. So I think from a theoretical perspective you are good. From a practical perspective, the formulation may be difficult to estimate.

Personally, I do not recall ever estimating a model with mediating effects for (interaction between) latent variables, so I do not ...

Hi Katya,

If these are warnings you get after estimation, I would not worry about them. During the optimisation process the algorithm may try invalid parameter values (e.g. a negative g_first < 0). These will generate the warning, but the optimiser will be smart enough to try another value (i.e. a ...