On 11/02/09 18:46, Dylan Beaudette wrote:
On Wednesday 11 February 2009, GRASS GIS wrote:
#474: r.quantile: segfaults with percentile=100
---------------------+-----------------------------------------------------
- Reporter: hamish | Owner: [email protected]
Type: defect | Status: closed
Priority: major | Milestone: 6.4.0
Component: Raster | Version: svn-develbranch6
Resolution: fixed | Keywords: r.quantile
Platform: Linux | Cpu: x86-32
---------------------+-----------------------------------------------------
- Comment (by glynn):
Replying to [comment:4 hamish]:
> I notice that if you do 'quant=3' you only get 2 results, and 'quant=1'
gives no output. (all others do the same, report n-1)
> Is this intended because 3 bins will have two separators (at 33% and
66%), or is it a bug?
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?
Personally, I would prefer that min and max are also shown (like the
output with the -r flag). Otherwise you have to look for those values
somewhere else, and I do find it useful to have them.
Moritz
_______________________________________________
grass-dev mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-dev
