[R] What is ks.test saying?

Kjetil Kjernsmo kjetil.kjernsmo at astro.uio.no
Thu Apr 27 14:57:09 CEST 2000


I have two matrices of equal dimension ll and lu that I want to do a
ks.test on corresponding rows in these matrices (dim(ll) is [1] 101 100).

If I do e.g. > ks.test(ll[50,],lu[50,])
just for testing, it displays a lot of numbers, and some more info:
[116] -3.000000e-02 -4.000000e-02 -4.000000e-02 -3.000000e-02 -4.000000e-02
[121] -3.000000e-02 -4.000000e-02 -3.000000e-02 -2.000000e-02 -3.000000e-02
[126] -2.000000e-02 -1.000000e-02 -3.469447e-18 -1.000000e-02 -3.469447e-18

	 Two-sample Kolmogorov-Smirnov test 

data:  ll[50, ] and lu[50, ] 
D = 0.11, p-value = 0.5806 
alternative hypothesis: two.sided 

Warning message: 
cannot compute correct p-values with ties in: ks.test(ll[50, ], lu[50, ]) 
The documentation doesn't discuss the output in any length, so I am
wondering what it tells me. The D is the test statistic if I've got it
right, and there is a p-value, but if I understand the warning, it isn't
exact. Is it possible to qualitatively say how it differs from the exact
p-value? And, what is the long vector that is printed?


Kjetil Kjernsmo
Graduate astronomy-student                    Problems worthy of attack
University of Oslo, Norway            Prove their worth by hitting back
E-mail: kjetikj at astro.uio.no                                - Piet Hein
Homepage <URL:http://www.astro.uio.no/~kjetikj/>
Webmaster at skepsis.no 

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