<p dir="auto">I'm a mathematician trying to plot several distributions (notably in this case Gamma and truncated Normal) in order to do some basic notebook-style exploration for different parameter choices. I first started with truncated normal, and after over half an hour, I still could not get scipy.stats.truncnorm to plot a simple normal distribution with mean = 18, standard distribution = 1.5, but truncated at 12 and 24. This includes after trying to follow the formula in the documentation for a and b - the behavior was always surprising, typically cutting the distribution in half and throwing it's support way beyond 24. I finally settled for just plotting a regular normal distribution when I couldn't get it to work.</p>
<p dir="auto">Now I'm messing around with the gamma distribution, and the API is again surprising. I would suggest that in the spirit of "batteries included", the user shouldn't have to do the sort of computations described in <a href="http://docs.scipy.org/doc/scipy/reference/tutorial/stats.html" rel="nofollow">http://docs.scipy.org/doc/scipy/reference/tutorial/stats.html</a>, shape parameter section, just to use the gamma distribution with its two typical parameters (k and theta, or alpha and beta, it doesn't matter - they are easy to translate between) as described on wikipedia <a href="https://en.wikipedia.org/wiki/Gamma_distribution" rel="nofollow">https://en.wikipedia.org/wiki/Gamma_distribution</a>.</p>
<p dir="auto">My request is that these standardized functions which lack a typical, full parameterization expose some kind of API allowing the user to specify all their typical parameters directly and get back a distribution with no further work required.</p>
<p dir="auto">scipy.stats defines univariate distributions in a standard form, with location and scale parameters. For some distributions, these do not agree with well with "common" parametrizations, which leads to confusion on various levels.</p>
<p dir="auto">It might be good to at least identify the most problematic cases and add some text to their docstrings. Possibly there might be a way of adding some actual conversion code(?)</p>
<p dir="auto">(cross-ref: <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="58096266" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/4533" data-hovercard-type="pull_request" data-hovercard-url="/scipy/scipy/pull/4533/hovercard?comment_id=75260691&amp;comment_type=issue_comment" href="https://github.com/scipy/scipy/pull/4533#issuecomment-75260691">#4533 (comment)</a>)</p>
<p dir="auto">Likely suspects:</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> lognormal (<a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="96439765" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/5075" data-hovercard-type="pull_request" data-hovercard-url="/scipy/scipy/pull/5075/hovercard" href="https://github.com/scipy/scipy/pull/5075">gh-5075</a>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> exponnorm (done in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="58896819" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/4559" data-hovercard-type="pull_request" data-hovercard-url="/scipy/scipy/pull/4559/hovercard" href="https://github.com/scipy/scipy/pull/4559">gh-4559</a>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> nbinom</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> rice (<a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="60154835" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/4605" data-hovercard-type="pull_request" data-hovercard-url="/scipy/scipy/pull/4605/hovercard" href="https://github.com/scipy/scipy/pull/4605">gh-4605</a> for a specific issue and a suggestion for how to fix) EDIT: done in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="60288259" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/4611" data-hovercard-type="pull_request" data-hovercard-url="/scipy/scipy/pull/4611/hovercard" href="https://github.com/scipy/scipy/pull/4611">gh-4611</a></li>
</ul>