likelihood warnings added to validate_task

[alexnakagawa]

Hi Jeremy,

As per #42 , I've added some code to the validate_task function in Likelihood.R that will do the following:

1. Find all of the variable types in a factor_list
2. check for whether there exists a "continuous" variable for a "density" outcome.
3. If both are true, then a warning() is thrown.

Please let me know if you'd like me to write tests, as well as update the reference website with the added warning.

[jeremyrcoyle]

Hi Alex,

It's more complicated than checking if there is a combination of density and mean type nodes in the same likelihood. That combination is not a problem.

The issue is using bounding with density type nodes. See the example in the issue. The user defines an NPSEM with a Y node that has variable type variable_type('continuous', bounds = bounds) (this is a a bounded continuous variable). He also defines a likelihood with a corresponding Y node that is of the density type: define_lf(LF_fit, "Y", lrnr_glm) (the default type is "density"). This combination doesn't work. So, what's needed is to check for nodes where the likelihood is density type and the npsem variable type is bounded continuous.

This check can be added to the validate_task function defined here: https://github.com/tlverse/tmle3/blob/master/R/Likelihood.R#L53, as that function has access to both the likelihood factor list (self$factor_list) and the corresponding npsem (via tmle_task$npsem).

[alexnakagawa]

Thanks for the clarification! Would it be sufficient to check for whether the "Y" node is of variable_type$type == "continuous? Or would there be cases where we'd have to check the "A" node?