R-sig-ecology Digest, Vol 20, Issue 3

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Today's Topics:

? 1. Re: Testing "order" on predicted data (Corrado)


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Message: 1
Date: Wed, 4 Nov 2009 16:21:27 +0000
From: Corrado <ct529 at york.ac.uk>
Subject: Re: [R-sig-eco] Testing "order" on predicted data
To: Sarah Goslee <sarah.goslee at gmail.com>, r-sig-ecology at r-project.org
Message-ID: <200911041621.27945.ct529 at york.ac.uk>
Content-Type: Text/Plain; ?charset="iso-8859-1"

Dear Sarah,

I do not understand the question.

I am not looking for any relationships between data, only rank order
correspondence, which means the nearer is the rank order equivalence the
better it is. I have tried to explain in my 2 emails, probably failing. The
number of variables is normally one, as in my second email.

I considered Kendal and Wilcoxon (and also Friedman), but I am not sure which
one is better (that is better at comparing rank orders).

Another example, to simplify the question: if you have ten judges evaluating
the quality of 10 products by ranking from the best (1) to the worst (10) and
you want to discover which couple of judges did provide the most similar
ranking for the products, which test would you use?

Best,

On Tuesday 03 November 2009 15:36:59 Sarah Goslee wrote:

You really don't give enough information - what's "better"? Are you
looking for linear relationships? Single variables or many?

Without knowing anything else, I think you might try looking at
Spearman (rank) correlations.

Sarah

On Tue, Nov 3, 2009 at 7:36 AM, Corrado <ct529 at york.ac.uk> wrote:

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,
--
Corrado Topi

--
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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