[R] plot confidence limits of a regression line - problem

Eik Vettorazzi E.Vettorazzi at uke.uni-hamburg.de
Mon Mar 9 11:30:10 CET 2009


Hi,
the predict-function is not very good in guessing names from a given new 
dataset. So if you want to predict x1 from some new x2 values, your 
newdata argument should contain some x2 - values.

predict(model, newdata=data.frame(x2=seq(0,4)), interval =  
c("confidence"), level = 0.90,type="response")

without that, predict uses your old x2 values and issues a warning message.


Martin Batholdy schrieb:
> hi,
>
>
> I don't know what I am doing wrong,
>
> but with that code;
>
>
> x1 <- c(1.60, 0.27, 0.17, 1.63, 1.37, 2.00, 0.90, 1.07, 0.89, 0.43,  
> 0.37, 0.59,
> 0.47, 1.83, 1.79, 0.90, 0.72, 1.83, 0.23, 1.97, 2.03, 2.19, 2.03, 0.86)
>
> x2 <- c(1.30, 0.24, 0.20, 0.50, 1.33, 1.87, 1.30, 0.75, 1.07, 0.43,  
> 0.37, 0.87,
> 1.40, 1.37, 1.63, 0.80, 0.57, 1.60, 0.39, 2.03, 1.90, 2.07, 1.93, 0.93)
>
> model <- lm(x1 ~ x2)
>
> predict(model, newdata=data.frame(x=seq(0,4)), ,interval =  
> c("confidence"), level = 0.90,type="response")
>
>
>
>
> I get an error message saying "newdate has four lines, but the  
> variable found has 24"
>
>
> what is wrong in the code?
>
>
> thanks!
> 	[[alternative HTML version deleted]]
>
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-- 
Eik Vettorazzi
Institut für Medizinische Biometrie und Epidemiologie
Universitätsklinikum Hamburg-Eppendorf

Martinistr. 52
20246 Hamburg

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