Repository: statsmodels/statsmodels

Issue:
Add interpretations for different method in the doc of LogitResults.get_margeff
I suggest that we can add the interpretations for different `method` in the [doc](http://www.statsmodels.org/devel/generated/statsmodels.discrete.discrete_model.LogitResults.get_margeff.html#statsmodels.discrete.discrete_model.LogitResults.get_margeff) of `LogitResults.get_margeff`.

![Snipaste_196](https://user-images.githubusercontent.com/33796896/58669329-d26fd700-8309-11e9-9dc9-26afb1106e2b.png)

https://www.stata.com/manuals13/rmargins.pdf




Discussion:
PRs welcome. Perhaps in Notes rather in the parameters docstring. 
@bashtage Would it be a good idea to add a new label like "PR Wanted" or something to the issues in case that folks want to contribute. 
Thie label idea sounds like a good one.  Making it easier for would-be contributors to identify what is actionable would encourage more first-timers.
Is anybody working on this?
Can I work on it?
@joybhallaa Please do.
@bashtage, @StevenLi-DS  , the link in the first comment is broken, and I can't find the documentation for `LogitResults.get_margeff` 
http://www.statsmodels.org/devel/generated/generated/statsmodels.discrete.discrete_model.LogitResults.get_margeff.html




On Wed, Aug 14, 2019, 10:23 Joy Bhalla <notifications@github.com> wrote:

> @bashtage <https://github.com/bashtage>, @StevenLi-DS
> <https://github.com/StevenLi-DS> , the link in the first comment is
> broken, and I can't find the documentation for LogitResults.get_margeff
>
> —
> You are receiving this because you were mentioned.
> Reply to this email directly, view it on GitHub
> <https://github.com/statsmodels/statsmodels/issues/5811?email_source=notifications&email_token=ABKTSRI425NRDDPWN4FQDXDQEQPOXA5CNFSM4HRNBWJKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD4JE4TY#issuecomment-521293391>,
> or mute the thread
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> .
>

I'm sorry, I can't work on this issue as I am swamped with Univ & an internship.

@bashtage , I would like to take this one if it's free. 
I think maybe mentioning the effects in docstring and writing some additional notes as in STATA for further info
Would you like me to assign it to you?
Please, go ahead

Resolving patch:
diff --git a/statsmodels/discrete/discrete_model.py b/statsmodels/discrete/discrete_model.py
--- a/statsmodels/discrete/discrete_model.py
+++ b/statsmodels/discrete/discrete_model.py
@@ -3593,7 +3593,8 @@ def get_margeff(self, at='overall', method='dydx', atexog=None,
             Note that tranformations are done after each observation is
             calculated.  Semi-elasticities for binary variables are computed
             using the midpoint method. 'dyex' and 'eyex' do not make sense
-            for discrete variables.
+            for discrete variables. For interpretations of these methods
+            see notes below.
         atexog : array_like, optional
             Optionally, you can provide the exogenous variables over which to
             get the marginal effects.  This should be a dictionary with the key
@@ -3620,8 +3621,15 @@ def get_margeff(self, at='overall', method='dydx', atexog=None,
 
         Notes
         -----
+        Interpretations of methods:
+        - 'dydx' - change in `endog` for a change in `exog`
+        - 'eyex' - proportional change in `endog` for a proportional
+          change in `exog`
+        - 'dyex' - change in `endog` for a proportional change in `exog`
+        - 'eydx' - proportional change in `endog` for a change in `exog`
         When using after Poisson, returns the expected number of events
         per period, assuming that the model is loglinear.
+
         """
         from statsmodels.discrete.discrete_margins import DiscreteMargins
         return DiscreteMargins(self, (at, method, atexog, dummy, count))


Test patch: