# [R] linear correlation?

Setzer.Woodrow@epamail.epa.gov Setzer.Woodrow at epamail.epa.gov
Thu Mar 7 16:16:57 CET 2002

Perhaps I've led a sheltered life, but my own experience leads me to
question the logic behind an analysis that leads me to want to compute
correlations between vectors in which the elements have different units;
cm and kg are not generally interconvertible!

R. Woodrow Setzer, Jr.                                            Phone:
(919) 541-0128
Experimental Toxicology Division                       Fax:  (919)
541-5394
Pharmacokinetics Branch
NHEERL MD-74; US EPA; RTP, NC 27711

dechao wang
<dechwang at yahoo.co.u        To:     r-help at stat.math.ethz.ch
k>                          cc:
Sent by:                    Subject:     [R] linear correlation?
owner-r-help at stat.ma
th.ethz.ch

03/07/02 05:33 AM

Hi, I have checked statistic textbooks about
correlations, but I am still not sure the correlation
analysis with different units, for example,

x1<-c(1,  2,  3,   100, 200, 300)
x2<-c(1.1,2.8,3.3, 108, 209, 303)
the unit of the first 3 numbers is cm
the unit of the last 3 numbers is kg

cor(x1,x2)=0.999655

Can I explain the correlation coefficient as normal in
which all numbers have the same unit?

Secondly, if keep the three large numbers unchanged,
just change the three small numbers, the coefficient
changes little, this means that the variation of three
small numbers is hidden by the three larger numbers.
Is there any solution in R to solve this issue?

Thanks,

Dechao

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