R help - Dec 2004 - spearman correction

Dear All !

Who knows which correction (by tied numbers) is used by Spearman-test in
function cor.test (e.g. cor.test(a,b,method="spearman"))?

a	b
12	135
13	153
15	144
17	180
18	162
19	198
20	234
21	225
25	270
26	261

rs(corrected)=rs(uncorrected)= 0.951515152

a	b
12	135
13	153
15	144
17	180
18	180
19	180
20	180
21	225
21	270
21	261

rs(corrected)= 0.943208012
rs(uncorrected)= 0.945454545


Thanks!

With best regards

Branimir K. Hackenberger

On Wed, 1 Dec 2004, Branimir K. Hackenberger wrote:
> Who knows which correction (by tied numbers) is used by Spearman-test in
> function cor.test (e.g. cor.test(a,b,method="spearman"))?
Anyone who reads the sources!  The critical line in cor.test.default is

             r <- cor(rank(x), rank(y))

so it uses rank(), and that averages ranks of tied observations.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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