The error you’re encountering is:

Erreur dans apollo_readBeta(apollo_beta, apollo_fixed, "MMNL_preference_space", :

INPUT ISSUE - File MMNL_preference_space_estimates.csv not found in working directory, nor in C:/Users/Val/Documents/.

This means that the apollo_readBeta() function is looking for a .csv file named MMNL_preference_space_estimates.csv, but it doesn’t exist in your working directory or in the specified output directory (C:/Users/Val/Documents/).

Why the Error Happens

• apollo_readBeta() by default expects a .csv file (not an .RData file) that contains estimated parameters from a previous model run.
• You have MMNL_preference_space_estimates.RData in the folder, but Apollo is not set up to read .RData in this function.

Solution Options

Option 1: Skip apollo_readBeta() if you’re not reloading estimates

If you’re running the model from scratch and do not need to load previous estimates, remove or comment out the line:

apollo_beta = apollo_readBeta(apollo_beta, apollo_fixed, "MMNL_preference_space", overwriteFixed = FALSE)

Option 2: If you want to reuse previous estimates

You need a .csv file with the estimated parameters, like the one Apollo usually writes after estimation (e.g., MMNL_preference_space_estimates.csv). You can do this:

Option 3: Manually convert .RData to .csv

If your .RData file (MMNL_preference_space_estimates.RData) already contains the estimated parameters, you can manually save them as .csv like this:

load("MMNL_preference_space_estimates.RData")

# Assuming the object inside is named something like model or apollo_model

write.csv(model$estimate, "MMNL_preference_space_estimates.csv", row.names = FALSE)

After saving that .csv, you can use apollo_readBeta() as intended.

Summary

To fix the issue immediately:

• If you’re starting fresh, comment out this line:

apollo_beta = apollo_readBeta(apollo_beta, apollo_fixed, "MMNL_preference_space", overwriteFixed = FALSE)

• If you need previous estimates, make sure you have MMNL_preference_space_estimates.csv in the working directory or convert it from .RData.

Wow, quite a detailed specific answer by Floyd R.--perhaps its worthwhile taking him on as paid (out of your research grant) consultant!