How to handover R list object to R transform in Code Workbook

Question

I estimate a polr model with R in foundry code workbook. After estimation I want to handover the model object to another R transform. Estimation works fine. Handover not.

Example:

global code

library(MASS)

transform code

model <- function(modeldata) {
    df <- modeldata
   
    model = polr(answer ~  eos_ratio,
                 data = df,
                 Hess = TRUE)

    return(model)
}

Error message

Function should return a data frame or FoundryObject or NULL.

Thanks

Answer 1

When you return something from Code Workbooks in Foundry, it's expected for you to be returning a data frame, a FoundryObject or a raw file written to a dataset. For saving down models, users generally use Foundry Machine Learning (FoundryML) but it currently doesn't support R officially. Please contact support for the specifics and if you face issues since I realize there might be a lot of pain here.

My R is a bit rusty, but there are a couple of (hacky) alternatives:

From the documentation https://www.palantir.com/docs/foundry/code-workbook/transforms-unstructured/#unstructured-files-in-r , here is how you save down a .rds file:

write_rds_file <- function(r_dataframe) {
    output <- new.output()
    output_fs <- output$fileSystem()
    saveRDS(r_dataframe, output_fs$get_path("my_RDS_file.rds", 'w'))

}

You can something similar with rda: Reusing a Model Built in R

The other option is store the model parameters in a dataframe: How do I store lm object in a data frame in R

You can then recreate the model using those parameters.