R help - May 2015 - Drawing the regression line and the 95% confidence intervals

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

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
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.