[R] testing slope

[Warnes, Gregory R]

For testing the hypothesis

	Beta[X] + Beta[Vn3] + Beta[X:Vn3] = 0

you can use the estimable function from the gregmisc package:

	estimable(m2, c("Intercept"=0,
			   "X"=1,
			   "Vn2"=0,
			   "Vn3"=1,
                     "X:Vn2"=0,
			   "X:Vn3"=1)
		    )

See the estimable help page for details.

-Greg




> -----Original Message-----
> From: Ronaldo Reis Jr. [mailto:chrysopa at insecta.ufv.br]
> Sent: Tuesday, February 04, 2003 2:51 PM
> To: R-Help
> Subject: [R] testing slope
> 
> 
> Hi all,
> 
> I try to test a linear slope using offset.
> 
> I have:
> 
> > m2 <- glm(Y~X*V)
> > summary(m2)
> 
> Call:
> glm(formula = Y ~ X * V)
> 
> Deviance Residuals: 
>      Min        1Q    Median        3Q       Max  
> -2.01688  -0.56028   0.05224   0.53213   3.60216  
> 
> Coefficients:
>             Estimate Std. Error t value Pr(>|t|)    
> (Intercept)   1.3673     0.8476   1.613 0.119788    
> X             4.0235     0.1366  29.453  < 2e-16 ***
> Vn2           0.9683     1.1987   0.808 0.427131    
> Vn3           4.6043     1.1987   3.841 0.000787 ***
> X:Vn2         4.1108     0.1932  21.279  < 2e-16 ***
> X:Vn3        -4.0069     0.1932 -20.740  < 2e-16 ***
> ---
> Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 
> 
> (Dispersion parameter for gaussian family taken to be 1.53955)
> 
>     Null deviance: 15303.977  on 29  degrees of freedom
> Residual deviance:    36.949  on 24  degrees of freedom
> AIC: 105.39
> 
> Number of Fisher Scoring iterations: 2
> 
> It is clear that X slope is diferent of Zero.
> X             4.0235     0.1366  29.453  < 2e-16 ***
> 
> It is too clear that X:Vn2's slope is diferent of X's slope 
> and diferent of 
> Zero, because is greater than X'slope.
> X:Vn2         4.1108     0.1932  21.279  < 2e-16 ***
> 
> But, the X:Vn3' slope is different of X'slope, but not 
> necessarily different 
> of Zero.
> 
> How I make to introduce this parameter in a new model for 
> test? An offset only 
> with Vn3 slope???
> 
> I try:
> 
> m2 <- glm(Y~V*offset(0*X))
> m2 <- glm(Y~X*V+V*offset(0*X))
> m2 <- glm(Y~V:X+V*offset(0*X))
> 
> but neither work :((
> 
> Thanks for all.
> Ronaldo
> -- 
> If you live in a country run by committee, be on the committee.
> 		-- Graham Summer
> --
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