[Rd] hist.default documentation

[Duncan Murdoch]

Thanks, I've committed the change.

Duncan Murdoch

On 6/17/2005 10:30 AM, Deepayan Sarkar wrote:
> On 6/17/05, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
>> 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?
> 
> Not mentioning it is fine.
> 
>> > (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".
> 
> Actually, I missed the remark just below this:
> 
>           In the last three cases the number is a suggestion only.
> 
> so this is fine as it is.
> 
>> > I'll be happy to provide a patch if these changes are considered reasonable.
>> 
>> Please do.
> 
> Here's the output of svn diff. Is this a reasonable way of providing a patch?
> 
> Index: hist.Rd
> ===================================================================
> --- hist.Rd     (revision 34748)
> +++ hist.Rd     (working copy)
> @@ -28,9 +28,9 @@
>    }
>    \item{freq}{logical; if \code{TRUE}, the histogram graphic is a
>      representation of frequencies, the \code{counts} component of
> -    the result; if \code{FALSE}, \emph{relative} frequencies
> -    (\dQuote{probabilities}), component \code{density},
> -    are plotted.   Defaults to \code{TRUE} \emph{iff} \code{breaks} are
> +    the result; if \code{FALSE}, probability densities, component
> +    \code{density}, are plotted (so that the histogram has a total area
> +    of one).  Defaults to \code{TRUE} \emph{iff} \code{breaks} are
>      equidistant (and \code{probability} is not specified).}
>    \item{probability}{an \emph{alias} for \code{!freq}, for S compatibility.}
>    \item{include.lowest}{logical; if \code{TRUE}, an \code{x[i]} equal to
> 
> Deepayan