Important: Read this before posting to this forum

  1. This forum is for questions related to the use of Apollo. We will answer some general choice modelling questions too, where appropriate, and time permitting. We cannot answer questions about how to estimate choice models with other software packages.
  2. There is a very detailed manual for Apollo available at http://www.ApolloChoiceModelling.com/manual.html. This contains detailed descriptions of the various Apollo functions, and numerous examples are available at http://www.ApolloChoiceModelling.com/examples.html. In addition, help files are available for all functions, using e.g. ?apollo_mnl
  3. Before asking a question on the forum, users are kindly requested to follow these steps:
    1. Check that the same issue has not already been addressed in the forum - there is a search tool.
    2. Ensure that the correct syntax has been used. For any function, detailed instructions are available directly in Apollo, e.g. by using ?apollo_mnl for apollo_mnl
    3. Check the frequently asked questions section on the Apollo website, which discusses some common issues/failures. Please see http://www.apollochoicemodelling.com/faq.html
    4. Make sure that R is using the latest official release of Apollo.
  4. If the above steps do not resolve the issue, then users should follow these steps when posting a question:
    1. provide full details on the issue, including the entire code and output, including any error messages
    2. posts will not immediately appear on the forum, but will be checked by a moderator first. This may take a day or two at busy times. There is no need to submit the post multiple times.

Delta method in Apollo on absolute difference

Ask questions about post-estimation functions (e.g. prediction, conditionals, etc) or other processing of results.
Post Reply
fayyazkhan
Posts: 6
Joined: 27 Apr 2020, 01:42

Delta method in Apollo on absolute difference

Post by fayyazkhan »

Hi Stephane,

I am estimating a model on a dataset, and estimating parameters for gains and losses in travel time (similar to the one in your paper: Asymmetric preference formation in willingness to pay estimates in discrete choice models).

In your paper, you estimated the below t-ratio for the difference by considering the absolute values. Would it possible to estimate this t-ratio in Apollo?

I tried the below delta method, but I believe it does not consider the absolute value.
deltaMethod_settings=list(operation="diff",parName1="bgain",parName2="bloss")
apollo_deltaMethod(model, deltaMethod_settings)


Best,
Fayyaz

Image
Attachments
delta method for t-ratio of diff.PNG
delta method for t-ratio of diff.PNG (80.54 KiB) Viewed 4795 times
stephanehess
Site Admin
Posts: 974
Joined: 24 Apr 2020, 16:29

Re: Delta method in Apollo on absolute difference

Post by stephanehess »

Hi Fayyaz

you can do this easily with the additional setting multPar1 or multPar2

deltaMethod_settings=list(operation="diff",parName1="bgain",parName2="bloss",multPar1=-1)

Check the help file/manual for more details but this should work

Stephane
--------------------------------
Stephane Hess
www.stephanehess.me.uk
fayyazkhan
Posts: 6
Joined: 27 Apr 2020, 01:42

Re: Delta method in Apollo on absolute difference

Post by fayyazkhan »

Many thanks for this, Stephane. It works perfectly.

Fayyaz
Post Reply