Drawing the regression line and the 95% confidence intervals

Dear Jim,

I really thank you lots, it perfectly works !
The reproducible example is below.

Last thing : I can easily get the predictions intervals but I don't get to
draw them.
If I want to draw on the same graph (the one I already have the confidence
intervals) the prediction intervals. I have tried the abline function
without success. How can I do ?

GDP.per.head=c(600,560,340,560,580,300,570,900,680,290,590,340)
Quality.score=c(4.5,6.5,6,4.5,7,3,9,10,12.5,6.5,7,9)
Competitivness.score=c(1000,1200,1400,700,680,1010,340,560,690,500,690,460)
LinearModel.1=lm(GDP.per.head ~ Quality.score + Competitivness.score)

plot(GDP.per.head, fitted(LinearModel.1),ylim=c(200,800))
devlm1<-lm(fitted(LinearModel.1)~GDP.per.head)
abline(devlm1)
conflm1<-confint(devlm1)
abline(coef=conflm1[,1],lty=2)
abline(coef=conflm1[,2],lty=2)
predict(LinearModel.1, interval = "prediction")

Many thanks once more for your help.
Sacha


----- Mail original -----
De : Jim Lemon <drjimlemon at gmail.com>
? : varin sacha <varinsacha at yahoo.fr>
Cc : R-help Mailing List <r-help at r-project.org>
Envoy? le : Mercredi 6 mai 2015 1h02
Objet : Re: [R] Drawing the regression line and the 95% confidence
intervals

Hi Sacha,
The line you have requested is off the plot. The following will
produce what I think you are asking, but I cannot speak for whether it
means anything sensible.

plot(GDP.per.head, fitted(LinearModel.1),ylim=c(200,800))
devlm1<-lm(fitted(LinearModel.1)~GDP.per.head)
abline(devlm1)
conflm1<-confint(devlm1)
abline(coef=conflm1[,1],lty=2)
abline(coef=conflm1[,2],lty=2)

Jim



On Wed, May 6, 2015 at 8:01 AM, varin sacha <varinsacha at yahoo.fr> wrote:

Hi, Dear R-helpers,

Here below you will find a reproducible fictitious example working

except the "abline" function.

First thing : I try to draw the regression line (multiple linear

regression). I try the "abline" function but it does not work. I don't get
any error message but the straight line does not appear on the scatterplot.

Second thing : I try to draw the 95% confidence intervals on the

regression line. How could I do ?

Using abline(0,1), I can of course add a line 45 degrees angle passing

through the origin (intercept=0 and slope=1), but it is not what I am
looking for.

GDP.per.head=c(600,560,340,560,580,300,570,900,680,290,590,340)
Quality.score=c(4.5,6.5,6,4.5,7,3,9,10,12.5,6.5,7,9)

Competitivness.score=c(1000,1200,1400,700,680,1010,340,560,690,500,690,460)

LinearModel.1=lm(GDP.per.head ~ Quality.score + Competitivness.score)
plot(GDP.per.head, fitted(LinearModel.1))
abline(GDP.per.head, fitted(LinearModel.1))

Thanks for your help. Looking forward to reading you.

Sacha