[R] testing slopes

[Dimitris Rizopoulos]

two options are to use an offset term or the linear.hypothesis()  
function from package car, e.g.,

y <- rnorm(100, 2 - 1 * (x <- runif(100, -3, 3)), 3)
############
fit0 <- lm(y ~ 1 + offset(-x))
fit1 <- lm(y ~ x)
anova(fit0, fit1)

library(car)
linear.hypothesis(fit1, c("x = -1"))


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
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Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
      http://www.student.kuleuven.be/~m0390867/dimitris.htm


Quoting Indermaur Lukas <Lukas.Indermaur at eawag.ch>:

> Hello
> Instead of testing against 0 i would like to test regression slopes   
> against -1. Any idea if there's an R script (package?) available.
>
> Thanks for any hint.
> Cheers
> Lukas
>
>
>
>
> °°°
> Lukas Indermaur, PhD student
> eawag / Swiss Federal Institute of Aquatic Science and Technology
> ECO - Department of Aquatic Ecology
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> CH-8600 Dübendorf
> Switzerland
>
> Phone: +41 (0) 71 220 38 25
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