On 6/17/2005 8:58 AM, Deepayan Sarkar wrote:
> I think there are a couple of things in ?hist that are not quite as
> clear as they could be.
>
> (1)
>
> freq: logical; if 'TRUE', the histogram graphic is a representation
> of frequencies, the 'counts' component of the result; if
> 'FALSE', _relative_ frequencies ("probabilities"), component
> 'density', are plotted. Defaults to 'TRUE' _iff_ 'breaks'
> are equidistant (and 'probability' is not specified).
>
> Unless I'm missing something, the 'density' component is NOT relative
> frequency or 'probability' in any reasonable sense, country-specific
> biases notwithstanding, except in the very special case where
> all(diff(breaks) == 1). Thus, the above description is confusing and
> probably even wrong.
I agree.
> Also, it seems to me that hist cannot draw a relative frequency
> histogram at all (which is not a bad thing, but it's of course very
> important to the undergrads we're teaching intro stats and R to). This
> should be explicitly mentioned.
I'm not sure about this. Is it really worth mentioning something if you
can't do it? Are you thinking of just giving a reference to barplot?
> (2)
>
> breaks: one of:
>
> ...
> * a single number giving the number of cells for the
> histogram,
> ...
>
> This is not quite true. 'breaks' is used in 'pretty', so it's more a
> suggestion than an exact specification. I'm not sure whether or not
> the behaviour should be changed (what's the point of having ``pretty''
> breakpoints anyway?), but if not, the documentation should be
> clarified.
I like the pretty breakpoints. It is good to label the breakpoints, and
ugly to have labels at other than pretty points. I'd clarify by
changing "giving" to "suggesting".
> I'll be happy to provide a patch if these changes are considered reasonable.
Please do.
Duncan Murdoch
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