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Apollo_deltaMethod expression for non-model parameters

Ask questions about post-estimation functions (e.g. prediction, conditionals, etc) or other processing of results.
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Bob123
Posts: 9
Joined: 20 Jun 2023, 13:39

Apollo_deltaMethod expression for non-model parameters

Post by Bob123 »

Dear Stephane,

I am using the Apollo_deltaMethod to calculate SE for Marginal Rates of Substitution between a continuous variable (time) and a categorical variable with levels ("high", "moderate", "low" and "very low"(the reference category).

I have used the delta method in Apollo to give me MRS between the "high", "moderate", and "low" versus base levels ("very low") of my categorical variable but would also like to use it to calculate the MRS between categories i.e. "high" versus "moderate". However, I can see in the manual that "An expression can only contain model parameters".

Is there an efficient way to do this in Apollo so that the output comes together (i.e., to write it into the expressions)? If I am correct the other way to do it would be to either change my ref. category (base categorical level) in Apollo_fixed or to somehow define a new variable before Apollo_probabilities as the difference between categories i.e. b_CERT_high-b_CERT_moderate?

Currently, I have the code below (which works), but I would like to obtain MRS and SE estimates for going from Moderate to High on WAIT.

Code: Select all

apollo_deltaMethod(model,
                   deltaMethod_settings = list(printPVal = 2,
                     expression=c(b_CERT_low_WAIT="b_CERT_low/b_WAIT*12",
                                  b_CERT_moderate_WAIT="b_CERT_moderate/b_WAIT*12",
                                  b_CERT_high_WAIT="b_CERT_high/b_WAIT*12"
                                  )))
Thanks in advance,

Rob
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stephanehess
Site Admin
Posts: 998
Joined: 24 Apr 2020, 16:29

Re: Apollo_deltaMethod expression for non-model parameters

Post by stephanehess »

Hi

wouldn't this just be:

apollo_deltaMethod(model,
deltaMethod_settings = list(printPVal = 2,
expression=c(b_CERT_high_vs_moderate_WAIT="(b_CERT_high-b_CERT_moderate)/b_WAIT*12"
)))
--------------------------------
Stephane Hess
www.stephanehess.me.uk
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