[R-sig-eco] Testing "order" on predicted data
Corrado
ct529 at york.ac.uk
Tue Nov 3 16:40:11 CET 2009
Dear friends,
the data are ordered real numbers between 0 and 1. something of that sort:
observations
site4 0.3
site1 0.4
site5 0.42
.
.
.
siten 0.999
after being sorted. I would like the models to order the sites in the same
order, even if the values are not right.
That is ideally:
model1
site4 2.4
site1 2.8
site5 4.0
.
.
.
siten 32
As you see, the values are different, but the order is still the same, that is
if I sort the values, I still get the same sorting order.
1) I do not understand how to use AIC, ROC or Spearmann in this situation!?
Could you pleas explain?
2) I had thought about using Kendal or Wilcoxon. What do you think?
Regards
On Tuesday 03 November 2009 14:49:32 Aitor Gastón wrote:
> You can compute Spearman's rank correlation coefficient using cor() between
> predicted and observed values for each model and test differences.
>
>
>
> If observed data are binary and the predictions probabilities, you may use
> a discrimination statistic like Somers' Dxy Rank Correlation or receiver
> operating characteristic curve area using somers2() in Hmisc package.
>
>
>
> Hope this helps,
>
>
>
> Aitor
>
>
>
> ----- Original Message -----
> From: "Corrado" <ct529 at york.ac.uk>
> To: <r-sig-ecology at r-project.org>
> Sent: Tuesday, November 03, 2009 1:36 PM
> Subject: [R-sig-eco] Testing "order" on predicted data
>
> > Dear all,
> >
> > I have a strange situation:
> >
> > 1) I have some data that are associated with "sites"
> > 2) I have two models that predict the data on the "sites"
> > 3) I would like to understand which of the models predicts the order of
> > the
> > data better. In other words, I am not interested in the models predicting
> > the
> > values exactly, but only in predicting values that are in the same order
> > (smaller to bigger).
> >
> > What is the best test?
> >
> > PS: Does that make sense?
> >
> > Best,
> >
> > Global Climate Change & Biodiversity Indicators
> > Area 18,Department of Biology
> > University of York, York, YO10 5YW, UK
> > Phone: + 44 (0) 1904 328645, E-mail: ct529 at york.ac.uk
> >
> > _______________________________________________
> > R-sig-ecology mailing list
> > R-sig-ecology at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
>
--
Corrado Topi
Global Climate Change & Biodiversity Indicators
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: ct529 at york.ac.uk
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