[GRASS-dev] Re: [GRASS GIS] #474: r.quantile: segfaults with percentile=100

[Glynn Clements]

Dylan Beaudette wrote:

> >  It's intended so that quant=N gives "N-tiles", e.g. quant=4 gives
> >  quartiles, quant=10 gives deciles, etc. AIUI, the convention is not to
> >  include the endpoints, e.g. "quartiles" are given as 25%, 50%, and 75%.
> 
> Is this a convention? I am not a math/stats expert, but in R I see that the 
> convetion is to report it like this:
> 
> # generate some random data
> x <- rnorm(100)
> # compute quartiles:
> quantile(x)
>         0%        25%        50%        75%       100% 
> -2.1691897 -0.3627331  0.1307290  0.6652009  2.4798260 
> 
> # we can see that it includes the min/max:
> summary(x)
>     Min.  1st Qu.   Median     Mean  3rd Qu.     Max. 
> -2.16900 -0.36270  0.13070  0.07639  0.66520  2.48000
> 
> Is this just a display/semantics thing?

I don't have a statistics background, but I'm more familiar with
seeing e.g. 1st, 2nd, and 3rd quartiles, without the 0th and 4th
quartiles.

I can add the 0th and Nth quantiles if desired (i.e. quant=N gives N+1
values).

-- 
Glynn Clements <glynn at gclements.plus.com>