[SciPy-Dev] Working on the docstring for stats.distributions.rv_continuous.fit
Wed Jun 16 10:59:10 CDT 2010
On Wed, Jun 16, 2010 at 11:49 AM, David Goldsmith
> First, thanks for your help! :-)
> On Wed, Jun 16, 2010 at 7:19 AM, Skipper Seabold <firstname.lastname@example.org>
>> On Tue, Jun 15, 2010 at 8:38 PM, David Goldsmith
>> <email@example.com> wrote:
>> > Hi! IMHO, the descriptions of the *args & **kwds parameters of the
>> > Subject-referenced method are not very clear, so let me see if I
>> > understand
>> > correctly:
>> I agree and was having a look at this last week. Here's my take. I
>> would err on the side of verbose in these docs, as the stats docs seem
>> to be a general source of confusion from comments I've received off
>> list, though obviously Josef, Travis, and others would know the
>> details better than I.
>> > *args : float(s), optional
>> > If the distribution in question depends on n parameters, _excluding
>> > location and scale_, then *args may contain 0 to n floats, which are
>> > starting estimates for the corresponding parameters. No default
>> > value(s).
>> I would add a note that n can be found in the numargs attribute of the
>> > **kwds _may_ contain the following:
>> > loc : float, optional
>> > Starting estimate for the location parameter, no default.
>> > scale : float, optional
>> > Starting estimate for the scale parameter, no default.
>> If the extra args *and* loc *and* scale are not specified, then the
>> default starting estimates for loc, scale, and args are taken from the
>> distribution's _fitstart(data) method. I think it would make more
>> sense to take the defaults for ones that are not provided by the user
>> only, but this is not how the code reads at the moment as far as I can
> So I can ignore this comment, correct? If not, we once again have the
> issue: document desired/intended behavior, if that differs from extant
Yeah, you can ignore this comment. Anything the user gives is not thrown away.
>> > floc : bool, optional
>> > Hold the location parameter constant; default: False.
>> floc : float, optional
>> Hold the location parameter constant at the given value. Default:
>> Fit this parameter using the data.
> So does this override a value provided by loc? Is one supposed to not
> specify both loc and floc? What happens if one does? Is an exception
Yeah. If floc, or whatever is provided, then it is always passed to
nnlf (negative log likelihood that we are minimizing). So it's not
technically wrong to pass a starting loc, but it doesn't make any
difference for the fitting because it never gets used.
>> > fscale : bool, optional
>> > Hold the scale parameter constant; default: False
>> See above.
>> > fi : bool, optional
>> > Hold the i-th scale parameter constant; there may be up to len(args)
>> > of
>> > these; default: False
>> I would keep it as something like
>> f1...fn : float, optional
>> Hold shape parameter fi constant at the given value, where i may be
>> 1 to numargs of the distribution.
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