[R] Drawing the regression line and the 95% confidence intervals

varinsacha at yahoo.fr varinsacha at yahoo.fr
Thu May 7 01:09:41 CEST 2015 

Jim,
Perfect
Many thanks once more for your support...
Best regards 
SV

Envoyé de mon iPhone

Le 7 mai 2015 à 00:01, Jim Lemon <drjimlemon at gmail.com> a écrit :

> Hi Sacha,
> As Brian noted, you will have to expand the vertical axis. Here is one
> way to do it.
> 
> plot(GDP.per.head, fitted(LinearModel.1),ylim=c(-60,1200))
> 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")
> library(plotrix)
> predmat<-predict(LinearModel.1, interval = "prediction")
> dispersion(GDP.per.head,fitted(LinearModel.1),
> predmat[,3],predmat[,2],interval=FALSE)
> 
> You may want to do something about the overlapping points.
> 
> Jim
> 
> 
> On Thu, May 7, 2015 at 5:52 AM, David L Carlson <dcarlson at tamu.edu> wrote:
>> Something like this?
>> 
>> # Compute the prediction limits and get their range to set ylim=
>> plim <- predict(LinearModel.1, interval = "prediction")
>> rnge <- c(min(plim[ , 2]), max(plim[ , 3]))
>> plot(GDP.per.head, fitted(LinearModel.1),ylim=rnge)
>> 
>> # As before
>> 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)
>> 
>> # Plot the prediction limits
>> segments(GDP.per.head, plim[ , 2], GDP.per.head, plim[ , 3], col="gray")
>> 
>> -------------------------------------
>> David L Carlson
>> Department of Anthropology
>> Texas A&M University
>> College Station, TX 77840-4352
>> 
>> 
>> -----Original Message-----
>> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Cade, Brian
>> Sent: Wednesday, May 6, 2015 2:22 PM
>> To: varin sacha
>> Cc: R-help Mailing List
>> Subject: Re: [R] Drawing the regression line and the 95% confidence intervals
>> 
>> The prediction intervals are likely to be much wider than the confidence
>> intervals so you will need to be sure you scale the yaxis limits large
>> enough to see them.
>> 
>> Brian
>> 
>> Brian S. Cade, PhD
>> 
>> U. S. Geological Survey
>> Fort Collins Science Center
>> 2150 Centre Ave., Bldg. C
>> Fort Collins, CO  80526-8818
>> 
>> email:  cadeb at usgs.gov <brian_cade at usgs.gov>
>> tel:  970 226-9326
>> 
>> 
>> On Wed, May 6, 2015 at 12:59 PM, varin sacha <varinsacha at yahoo.fr> wrote:
>> 
>>> 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>
>>> À : varin sacha <varinsacha at yahoo.fr>
>>> Cc : R-help Mailing List <r-help at r-project.org>
>>> Envoyé 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.
>>> 
>>> ______________________________________________
>>> 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.
>> 
>>        [[alternative HTML version deleted]]
>> 
>> ______________________________________________
>> 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.
>> ______________________________________________
>> 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.

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