On Feb 12, 2009, at 10:00 AM, <grass-dev-request@lists.osgeo.org> <grass-dev-request@lists.osgeo.org > wrote:
Date: Wed, 11 Feb 2009 21:34:18 +0000
From: Glynn Clements <glynn@gclements.plus.com>
Subject: Re: [GRASS-dev] Re: [GRASS GIS] #474: r.quantile: segfaults
with percentile=100
To: dylan.beaudette@gmail.com
Cc: grass-dev@lists.osgeo.org
Message-ID: <18835.17498.645317.388349@cerise.gclements.plus.com>
Content-Type: text/plain; charset=us-asciiDylan 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 2.48000Is 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).
I agree with Glynn. I don't see the 0 and Nth quartile referred to. They are simply the min and max, which seem easier for most people to understand too.
Michael